The party members in games that have them tend to be less useful than they ought to be. While the characters' involvement in the story is generally pretty good, using them in battle is much more iffy.
Firstly, it seems like a Heartless or a Nobody so much as breathing in the same room as a CPU character is enough to kill them. It's much more noticeable in Kingdom Hearts II, where the boss fights are more dynamic. You can heal them, but they'll just go down two seconds later, so it's not worth the trouble. Not that there are any consequences to the party members dying anyways, since they'll just get back up after a few seconds on their own. The main character (usually Sora) is the only person who causes a Game Over if they go down. A few of the Limit Breaks and situational commands are pretty useful in certain circumstances, but for the most part, it's not worth looking after your party members.
Secondly, Artificial Stupidity abounds in your party members. The first few Kingdom Hearts games especially are known for very dumb party AI; they'll frequently try attacks that won't work over and over (like using fire spells on fire-elemental Heartless, which does nothing to them), stay back for several seconds before charging in, and wasting all of their magic and items the moment any battle starts. You have very limited control over what a CPU party member does, usually just telling them which target to attack and nothing else. Even setting their behaviors in the Party menu doesn't seem to affect their behavior that much. They're at least tangentially useful in stun-locking enemies in trash mobs. But against bosses, they're all but useless.
Finally, you have no way of knowing when your allies will heal you. The most common scenario is when you're about to heal yourself, you'll discover too late that Donald or Goofy has already healed you with magic or an item. If the combined healing is more than your hit points would allow, this becomes a waste of resources. Worse still, you won't hear the character calling for Sora if you're too far away. And that's if they even decide to heal you at all; it's something of a meme in the fandom that Donald won't heal Sora with his magic in spite of being fully capable of it.
Kingdom Hearts III buffed the party quite a bit. They can now stagger humanoid bosses, which not only helps Sora combo the boss but also helps to keep the party from getting smacked mid-attack like they used to be. They're also much smarter about healing, know how to combo enemies. The removal of the Arbitrary Head Count Limit also helped, as you can have up to five people including Sora in a party at any one time. Several late-game party members are also extremely powerful; Roxas and Xion in particular are so Purposely Overpowered that they can solo Saix without Sora's interference. However, most of their defenses are still as paper-thin as ever. And the powerful Limit Breaks and Drive Forms have been replaced with Team Attacks, which are functionally random, so it's still a bit of a crapshoot. And even then, the most powerful Superbosses in the Re:Mind DLC have Sora fighting the battles alone, so none of this will help you in the game's hardest fights, where you'd need it the most.
In some of the games, you have to defeat bosses through a combo finisher or magic, no exceptions. You can equip skills that increase the length of your combos... and these combos can be interrupted while attacking. This might even potentially mean losing a fight because the boss didn't go down even though you were wailing on the boss's last bit of HP, because the attacks didn't count as a finishing move. While there's an ability in Kingdom Hearts II that allows you to use a finisher instantly in the middle of a combo, such a thing really shouldn't have been necessary.
Some abilities are so common that it's a wonder they're even optional, to the point that several are practically mandatory to complete the games. The thing that makes them Scrappy Mechanics is that they cost precious AP to equip, and considering how frequently they're used, it's a shame that AP has to be wasted to use them.
The Second Chance and Once More/Withstand Combo abilities have been criticized by some fans as crutches on the game's design, as many late-game bosses and Superbosses are balanced with those abilities in mind. The enemies deal so much damage that your regular Defense and Max HP stats do nothing to stop you from getting one-hit-killed anyway. This also turns situations where you can't obtain Second Chance/Once More (like with Zero Experience enabled) into a de facto No-Damage Run on top of everything else.
The Leaf Bracer ability is in a similar boat to Second Chance and Once More; when equipped, it makes you invincible while using a Cure command. There's really no reason not to have this on, and the late-game enemies in each title appear to be balanced with the expectation that you're going to have it on anyway.
A few titles have Scan, which shows enemy HP. Why a player would ever turn this off is anybody's guess; outside of a Self-Imposed Challenge, there's really no reason why you wouldn't want to see how much HP your enemies have left. Later in the series, Scan stopped being optional, but why such a thing would ever be optional is a mystery.
The original Kingdom Hearts was criticized for having unskippable cutscenes, which was especially irritating when they came before a difficult boss fight, forcing players to rewatch the scene each time they lost. Fortunately, the option to skip cutscenes was added in the game's Updated Re-releaseKingdom Hearts: Final Mix. All subsequent releases of the original Kingdom Hearts have also kept the option to skip the cutscenes, and every game after the first one lets you skip cutscenes by default, meaning this frustration only applies to the original PlayStation 2 release.
The first game's Gummi ship sections are widely hated for being slow-paced. While they're all rail shooters in the vein of Star Fox, there are too few enemies who attacked far too slowly for the sections to be any fun. Not helping matters was that until you obtain the Warp Gummi, you had to play through these segments every time you want to go to another world, which is a colossal waste of time. The developers thankfully fixed this by revamping the Gummi sections entirely for the sequels by making them much faster and more dynamic.
The camera system in Kingdom Hearts I has been half-jokingly referred to as an "anti-camera" because of how inexcusably bad it is. If the function of a camera is to show you what you need to see, the camera in Kingdom Hearts I seems determined to obstruct your view. A player might spend as much time fighting with the camera as they do fighting the Heartless due to the camera's tendencies to weirdly zoom in, get stuck on things, or just freeze in place. Locking onto a target helps somewhat, but not much. This gets especially bad in later levels like Monstro and Neverland, which feature very tight spaces that the camera will frequently get stuck on, forcing weird zooms and pans that obscure what's going on for several seconds at a time, taking your attention away from the fight. Frustratingly enough, the camera issues have not been fixed in any Updated Re-release, despite the camera being a chief complaint about the original Kingdom Hearts.
Atlantica's controls allow Sora and company to move around in 3-D space, but only by pressing buttons to swim up or down. It was hard enough just getting to where you wanted Sora and company to go. Neverland had similar mechanics with flight, but outside of one Superboss, flying wasn't a requirement since a player could still land and fight on the ground. Meanwhile, Atlantica featured two boss fights against Ursula, the first of which is considered That One Boss simply because of how hard it is to control Sora when your attention needs to be divided.invoked
The Trinity Emblems require Sora, Donald, and Goofy to activate them. And you needed to do this, because they usually contained valuable rewards or advanced the plot. Used any other party member? Have fun going all the way back to a save point to switch them out to activate this one emblem. Luckily, any issues with party line-up were confined to the original game; Kingdom Hearts II allows you to switch party members out at will when not in battle, III didn't have an Arbitrary Head Count Limit like the rest of the series, and neither II nor III had Trinity Emblems anymore.
One of the Trinity Emblems in Halloweentown was Permanently Missable Content in the original release - if it wasn't activated before the first Oogie Boogie boss fight, it was gone for good, locking you out of 100% Completion. This Emblem has been moved to a location that doesn't go away in every Updated Re-release, but such a thing really should have been caught in playtesting.
The card battle system drastically limits your combat freedom. It's not so bad when you fight normal enemies, but boss fights require a little more strategy. Sometimes, you'll run out of useful attack cards and would have to rely on Pluto to help you get more. It's even worse on Riku's story mode. His deck can't be customized like Sora's, so if you have a weak deck, you're stuck with it for the rest of the world. Unlike Sora, Pluto cards don't help him when he runs out. You can pretty much be stuck in a boss battle where your only reloadable card is a 1.
Any time you require specific-numbered map cards to access a room. You can only get map cards through battling the Heartless, and each card is randomly generated. If you don't have any roulette cards on hand, your only option is to constantly grind until you get that one specific number you need. It's especially awful near the end of the game; one room in particular requires a 1 blue card, 3 red card and then multiple cards totaling up to 99, which will likely necessitate even more grinding if you haven't stockpiled cards up to that point.
The Demyx fight has a mechanic that makes him That One Boss for the wrong reasons. You have a small amount of time to defeat some spawned water enemies, and not doing it in time is an instant game over. The final version of this attack requires you to kill all these enemies in only ten seconds, which is nigh impossible unless you can get the Reaction Command to fire off just right. The game provides no reason why you lose this fight for not killing all the spawned enemies fast enough. You just lose, tough luck, try again. And the game makes it appear as if Demyx is supposed to be a joke, with Jiminy's journal saying that that Demyx is "not very good at fighting". You thankfully only have to fight him once, but that one time is going to take a few tries because of this needlessly frustrating addition.
Atlantica's swimming controls were hated in Kingdom Hearts I, so for this game, it was replaced by a Rhythm Game. Too bad that this Rhythm Game is just as hated. Apart from the questionable quality of some of the songs, the mini-game itself is poorly-designed. The cues are only vaguely in line with the music, and there are so few of them that you spend the majority of each song just looking at the characters and doing nothing. And if you happen to pause the game at any point, you can't just pick back up from where you were; you have to do the entire song all over again. The whole thing is optional, but it nets you an upgrade to Blizzard magic, some equipment, and you need to complete it to unlock the Golden Ending. To make matters worse, this game has improved swimming controls that are significantly less awkward to use, so ditching the action combat for a rhythm game was not necessary.
The 3D control scheme was featured partially in Neverland when you gain the power of flight, but you get it at the end and it's not necessary to progress, per se. The fact that you can lock onto enemies, chests, and key items and automatically swim to their location made it moderately more tolerable. Then, in 358/2 Days, they bring the 3D mechanic back with messed up buttons but don't retain the lock-on shortcut - making fighting in mid-air incredibly irritating at best (and building a chain damn near impossible), considering how often flying enemies change their positions.
The mechanics for stealth missions in Days are a huge pain. When following Pete, you have to ensure that he remains in your field of vision, while you avoid going into his (which are Color-Coded for Your Convenience). This would be fine if the camera didn't hate you with a vengeance and if your partner didn't stand aimlessly so that he could get caught, because the game counts your AI partner being spotted as failing. Also, when segments of this mechanic are implanted into Beast's Castle, it gets rather tedious when you have to avoid being caught by either Lumière or Cogsworth. What really puts the cherry on top of this massive disaster is that even if you try to glide over them so that you're practically touching the ceiling, they can still see you.
Your "field of vision" has no connection with whether you can actually see your target. Instead of using the camera lock-on system, the game defines your field of vision as a short cone-shaped area directly in front of your character. That's right — the game completely ignores the mechanism that keeps your eye on a target for a mini-game involving keeping your eye on a target. So if you try to circle-strafe, the target leaves your vision area because the cone area turns sideways. You fail the mission because the game says you lost sight of your target, despite the fact they're five feet away and the camera has perfect vision of them.
While the new Command Deck allows for a wide variety of attacks, it's held back by flawed execution:
For starters, standard physical combos took a massive hit in comparison - they're awkward, weak, and just feel very loose. They can access powerful Finish Commands, but Command Style finishers are often much stronger.
Commands have a reload time in order to balance their use with combos, but that balance is completely shattered by the Haste abilities, which are very easy to obtain. Having all 5 Hastes makes commands reload faster than you can even use them, making combos even more worthless.
Commands. Ultimate commands have very slow animations and lack invincibility frames, which just leaves the player open when using them. This makes the hardest-to-obtain commands usually worthless. Meanwhile, the unassuming, yet invincibility-granting and powerful Thunder Surge is the best in the game, with few, if any drawbacks.
Unlike Kingdom Hearts II, which used a "Revenge Value" system to keep players from combo-ing bosses endlessly, but in a predictable and reactable manner, this game has bosses and even some standard enemies break out of hitstun at complete random, usually using an attack that becomes unavoidable if you were busy attacking. This is probably the second-biggest complaint about humanoid bosses, because it's simply counteractive to the combo-based system and punishes players for successfully finding openings.
You also can't directly affect when you enter a Command Style, so your character will automatically enter it once they can. They are invincible during the animation, but there's a brief period where you're vulnerable to attacks afterwards. Dying from entering a Command Style through no fault of your own is more likely than you'd think.
The movement in Birth By Sleep was very slow compared to the console games. While Terra, Ventus, and Aqua moved across fields pretty slowly, enemies would often be much faster. Combine that your slow attack movements, and you can easily fall into trouble.
A timer called the Drop Gauge forces the player to switch between Sora and Riku whenever it runs out. The problem is that it can drop during battles, including boss battles — and if you drop during a boss battle, it will regain all its health once you drop back. This can be helped by manually dropping or buying a consumable item that increases the drop gauge, but this won't help with the bosses regaining health, and the item requires you to waste a command slot to use it.
Dream Drop Distance also has the absolute WORST means of learning abilities: Dream Eaters. This can bite the player in the ass in many ways:
Each Dream Eater had many different abilities, and it's not clear at first glance who has what ability to teach your character. Many of the abilities are also stuck and assigned to the Dream Eaters, such as [element] screen/boost, meaning that if the Dream Eater leaves the party, Sora and Riku go without those passive benefits.
They all take an ungodly amount of DP to learn new abilities, but each enemy regardless of strength only gains one DP, and the minigames aren't much better or faster at it.
Dispositions. Each Dream Eater has a disposition that it can randomly change to in order to teach or learn new abilities. These change randomly and may or may not be the one you need to learn new abilities. It will be frustrating petting them or painting them or feeding them to change their attitudes, and then you have to hope its the correct disposition or you wasted your time and Munny.
If you change anything in the Command Deck menu, it resets EVERY command's time gauge. While it makes perfect sense to make any newly installed commands have to start charging from the beginning to prevent abuse, there's no reason why it should affect every command you're currently using. And worse, even if all you do is rearrange the order the commands are listed, it will still reset all of them. This makes the Drop system even more annoying, since if you want to refill the Drop meter you need to use an item. There's no reason to always have that item take up a command slot, but every time you switch it in, you'll end up resetting all of your gauges.
Failing at the cooking minigame with Little Chef/Remy costs you all the dish's ingredients, which gets infuriating when you consider that some ingredients can only be obtained from Flantastic 7 or Hundred Acre Wood minigames. You've either got to go all the way back to try again, or resort to Save Scumming.
The enemy lock-on refuses to work if your target isn't onscreen. This makes it unnecessarily difficult to find whatever you're trying to fight, especially if you're being shot at by a mook who's hiding in an elevated position. This is fixed in the 1.09 update, along with a number of other combat fixes included in the update.
For all of the new emphasis and free form exploration the Gummi Ships get, you don't actually have full 3D movement, much less any convenient way to loop or anything outside of a quick button command to reverse direction. Your ascent/descent caps at a certain angle, which is bad for huge spans of space with plenty of verticality. And if you're looking for item or blueprint crystals that happen to be in tight areas, this means you have to clumsily circle a few times and keep reorienting yourself to even shoot them.
Blocking is extremely hit-or-miss. The main problem comes from how the game counts combo attacks from enemies and how many invincibility frames it gives you as a result. This is easily seen when fighting against Marluxia, whose desperation move involves him cartwheeling his scythe in circles at Sora. In Kingdom Hearts II, the blocking was much more efficient and allowed you to block the attack as long as you got the timing right. Here, the game only counts a few hits from it as part of a combo before having Sora's block stop working and you get hit. Like the lock-on, blocking was adjusted in the 1.09 update.
