- Breather Boss: Bug Bug, both times.
- Demonic Spiders: If you ever run into an invisible enemy, prepare for pain.
- Any enemy with Run command resistance. This lowers the effectiveness of Run commands and naturally, late-game bosses have maximum Run resistance. Meaning unless you score a critical hit, you're going to do scratch damage to them.
- Game-Breaker: A few of them:
- Solar Pack, which heals robots with a small amount of HP per turn. Focus on defense and the robot becomes quite the tank. The only problem is it requires an Empty Pack which you can find one hidden away in Rococo Sewers. You can also find them as rare drops from a mob in a dungeon that is inaccessible if you beat it. A third way is to create Quick Pack and have the robot die. The pack will become an empty one.
- Add Boots 5 for even more ridiculousness. Said treads increase defense and evasion and add in a Shield 5 for a robot that even the last boss can't even touch. The only problem is Boots 5 makes your robot slow and shortens the movement range, but equip a Turbo Pack on it and that problem goes away.
- A maxed out Punch 3 is a weapon that frequently makes critical hits, turning most fights including bosses afterward into one or two Critical Hit Kill fights. Combine it with a high defense and a Shield 5 and you can pretty much just stand there next to the opponent and effortlessly punch your enemy to death.
- Goddamn Bats: Mole enemies in the volcano level. They randomly hide in the ground, making them invulnerable for that turn, have a screen-wide earthquake attack that not only damages you but destroys capsules, and use a melee attack designed to hit your back.
- Hilarious in Hindsight: A RPG game about a lone child protagonist going to save the world with a battle system about having said kid throw a red and white ball on the battlefield which explodes to free a being that the player then has fight for them. Are we talking about Robotrek or Pokémon? Made all the more amusing due to several Pokémon like Porygon that have a mechanized look and/or artificial origin.
- That One Attack: Confusion. Any enemy that can use it can lock you in a near-endless cycle of uncontrolled movement unless you save against it, which even a fully-upgraded robot cannot do reliably.
- That One Boss: Being an Enix game, the list of bosses that aren't in this category is smaller.
- Mamurana: She splits into clones and randomly swaps her position when she does so, making it annoying to actually do damage to her.
- Big Eye: He hurts. A lot. If you wasted your Scrap 9 on something other than Shield 4, this is effectively a stopping point in the game until grinding overtakes his power.
- Black Tank: Continues the trend that Big Eye started.
- DeRose: The poster child for this trope. She has the second highest amount of HP, a laser beam that can cause confusion, a nuke that does decent damage, and a headbutt attack that is basically instant death. Since she also has RUN resistance, unless you go in with a maxed out Punch weapon, the battle becomes one of attrition assuming you didn't spec out a robot for high evasion and defenses.
YMMV / Robotrek