YMMV / Infectonator!

• Demonic Spiders:
  • Secret Agents in World Dominator have a lot of health, shoot very quickly, kill zombies quickly, and worst of all, cannot be infected by your virus click!
  • Soldiers in World Dominator show up relatively early, shoot almost as fast, take a few hits to kill and are generally a slightly weaker version of the agent. They're not immune to the virus click however.
  • If you thought Secret Agents were bad, Infectonator 2 introduces Hazmat Guys. These are like Secret Agents but with more health, and even greater firepower.
  • Mages in Necronator. They deal huge damage over a very large range and have the same fire rate as archers, allowing them to kill your units and your base with great ease.
  • The Zombie Intervention and Tactics Squad (ZITS for short) in 3. They tank hits almost as much as a boss does, and have the most damaging weapons in the GAME. What's worse is that past a certain 'panic level' they appear in every single level. And then just when you've finally upgraded your zombies to match them (or you learn to leave out burgers for them), they upgrade again, sending TWO squads out every level and hitting even harder than before.
• Game-Breaker: Diablo in Necronator. Firstly, you can summon him anywhere instead of your portal, and he comes down as a meteor with splash damage. At max level (easy to do), he has a TON of health (more than 3x of any hero), has a lightning move that chains and deals huge damage (2 hits to kill an enemy hero), and his other attacks hurt a lot in general. Even with six heroes ganging up on you (like in the Abyss), he can take on all of them with some Freeze support. And if he dies, you can summon him again for the mere cost of 100 mana (most other heroes cost more than this). The only thing that prevents him from completely breaking the game is that you only obtain him in the third-to-last stage.
• Goddamned Bats:
  • Soldiers, who are able to fire at your zombies and kill them quickly if you don't upgrade your health.
  • Their Archer counterparts in Necronator are just as bad, being able to shoot quickly and mow down your melee hordes if there's a large group of archers.
• That One Boss:
  • Santa Claus in Infectonator 2. Not only can he do and take a lot of damage, he can also heal himself and the Mooks around him. To compound things further, almost all the Mooks in the area are Elite Mooks immune to regular infection and must be defeated in order to be infected!
  • Ramboo is another one. His rapid fire mows down zombies like a lawnmower over grass, and his triple grenade Spread Shot is a One-Hit Kill on any normal zombie, no matter the defence. You'll need to Zerg Rush him in order to have a chance at winning.