The Mook Horror Show for everyone piloting an MT or defensive measures beneath the titular AC units is a recurring trend throughout the games. A group tries to do a worker's strike under a corporation's watch? Here comes a highly deadly mercenary in a ridiculously powerful giant robot that can obliterate you and your co-workers in seconds with next to no effort for a paycheck. Often times, the games will depict their open radio chatter, as some of them think this is a good way to show how serious they are — only to start screaming and panicking as you slaughter them all.
Hell, the first two missions of the entire franchise consist of wiping out peaceful protesters or strikers, depending on which one you take. All these people simply wanted better lives for themselves and their peers - and for that, they're slaughtered to a man by a massive mech they have practically no hope of diverting, much less stopping, all at the behest of corporations that see them as expendable worker drones. Talk about setting the tone for the franchise.
The Arms Forts in For Answer are fully-staffed weaponized bases. They're terrifying as is, basically being gigantic weapons of mass destruction that singlehandedly create strangleholds on entire regions with their destructive power, but then the game makes it very clear as you blow through them how you've set fires ablaze inside their structures and killed off numerous members of staff inside. And, of course, inevitably all of them.
Anything relating to Human-Plus, which gives a pilot cybernetic upgrades... but generally damages their mind in the process, and its successor programs in the later games. You will usually have to fight or work with the pilots that went through this at least once a game. Some are Laughing Mad, some are Creepy Monotone, but they're all incredibly disturbing to listen to. One example is a re-made mission from the first game featured in Nexus, where a pilot begs you for help in attacking a train somehow related to the program. At the beginning, he's overly anxious. Once the train is destroyed, he turns on you, saying in a monotone voice: "Everything, yes. I must. Destroy. Everything."
Even worse, one mission has Chrome hire you to check out a supposedly-abandoned Murakumo research facility where Human-Plus experiments were conducted, but self-defense systems went berserk on the search. You get in there and the whole place is rusted and decayed, looking more like an abandoned prison than any of the cleaner labs in the game, and a Japanese broadcast is distorted and keeps playing in the background. The further you get in, the more strange knocking and rumbling sounds echo through the facility, and yet even after you clear out every single enemy, you never find out what's actually making that noise. And the mail that Chrome sends you after you retrieve a capsule from inside the facility? Human-Plus was from before the end of the surface world, and Murakumo were effectively experimenting on anyone that people wouldn't care if they went missing just to see if it worked.
The easiest way to be introduced to the Human-Plus creepiness? Fall into 50,000 credits of debt, which is easy if you quickly waste your ammo and run out of AP in a mission.
The first game, for example, abruptly gives you a Non-Standard Game Over if you ever hit that mark. You hear two researchers prepare to experiment on you solely because you're a failure of a Raven and got "volunteered" by force as a result. You get to start the game over with your AC and parts intact as well as new abilities and the plot acts like it never happened — but as far as the game is concerned, you all but died or were never seen again.
A recurring problem in the series is that A.I. Is a Crapshoot. From what happens in Nexus below, to DOVE/the Controller in 3 and IBIS in Silent Line trying to kill anyone that dares to try to leave Layered as its own systems start to fail, to the recurring Nine-Ball that is itself an AI running the original Raven's NEST that never quite seems to finally die until its Seraph form is downed. Humanity keeps messing itself up so bad that they leave their care in the hands of machines, and the machines almost invariably fail and nearly end the world yet again. And that's still a better option than leaving it in the hands of the cutthroat corporations that will kill everyone and each other, no real care for target discrimination or collateral that isn't a danger to their interests, to get their way.
If that isn't bad enough, there's the fact that you're the one that usually helps one of the factions or corporations seize control, if the story doesn't bottom out in a Greater-Scope Villain having to be taken down. Some random Raven or LYNX that, depending on the game, can go From Nobody to Nightmare in mere days as you disrupt the entire corporate warfare and upend the status quo, sometimes for good, sometimes potentially for bad. And rarely is it personal — you're usually just here for the previously-mentioned paycheck. Then you realize that every other pilot is the exact same thing; some have morals and draw their lines in the sand, but most don't, and others are just plain looking to pick a fight. These are the people that decide the fate of the world time and time again: mercenaries and corporate soldiers, rather than noble heroes.
At the end of Nexus, your character accidentally releases a mob of kamikaze drones that attack the world.. It cuts to your AC on the roof of an enclosed city, where you try to fight the entire mob by yourself. The screen slowly fades to black as your AC keeps calling out damage warnings.
For that matter, the later parts of the plot of Last Raven; amidst the conflict between the merged corporate power of The Alliance and the remaining Ravens of Vertex, the automated weapons that severely damaged humanity's standing on the surface of the Earth still exist as the Pulverizers, and in no time flat both the Alliance and the Vertex can be completely wiped out depending on your ending. The general ending most consider to be canon? You're truly the last Raven as every single other Raven was killed and the Alliance is destroyed, either by you or the Pulverizers.
RD and Chief going insane in AC 5. RD is seemly killed earlier on, but he is turned on you and suffers a major personality change in a matter of hours and is ready to kill his friends for no explainable reason. Chief, on the other hand, is an AI and, therefore, can't really be killed. He lives for battle and keeps coming back after seemly dying several time. He laughs madly every time you defeat him. Even when his AC explodes and is on fire, he pulls down a concrete support column and rushes you. Many of his attacks are one-hit-kills if you contacts with you just right. He just seems so happy while trying to beat your face in..
You later learn that Armored Core V and Armored Core Verdict Day are sequels of Armored Core For Answer. Let thatsink in for a second...
Expanded material puts the control system used in NEXTs as this in an And I Must Scream fashion- the system requires the pilot's nervous system to be hardwired into the control pod, or AMS. Which is good, because this allows the pilots to have near-zero latency in controlling their NEXT. They can just simply think of whatever movement or action they want their NEXT to perform, thus eliminating the need for numerous levers and switches and such. Which is also bad, because this virtually makes the NEXT an extension of their own body. This would explain how the NEXTs in 4 and For Answer seem to remain intact and in one piece despite being shot down. The destructive damage the mechs experience are translated into pain and felt directly by the pilots themselves. If you subject the NEXT to so much destructive force, you also subject the pilot to so much pain, which could make the pilot pass out or, in most cases, simply die inside the cockpit. Now, imagine what would happen if an active NEXT with a pilot inside had its arm blown off or be cut in half in the torso area. Or worse, have its head part ripped off...
In for Answer CUBE dies during Defend Line Ark when Fragile's experimental AMS overloads, basically frying his nervous system from the inside out. Sure, he may be a villain, but nobody deserves to die like that.
CUBE: Energy flow is reversing from the AMS! AAAAARGH!!
The Bio-Weapons that occasionally show up throughout the series. The AMIDAs, in particular.
Armored Core V has a few pretty scary moments, despite being a game about controlling a giant mecha. During the first Story mission, it's pretty much made clear that if you don't do your job well enough, Father can and will have you destroyed. That is, provided the enemy doesn't beat him to it. Later, it is revealed that the bad guys are willing to kill anyone or even start a war inside a highly populated city... FOR ENTERTAINMENT!
