Oh oh oh! Megaman 1, Elec Man if you don't have cutman's weapon.
His attack is instant, has a huge hitbox and kills you in 3 hits! And he takes like 20 hits to kill and is really fast! What the FUCK?
You know, this happened to me when I was just casually playing through the series and it was one of the few places where I really had to abuse save states because he can 3-shot you and sometimes you think you are above the attack when you are standing on the platform but guess again you are not BOOM 1/3 of hp gone.
But it wasn't as gay as the HYPNO DISC RACE level in battletoads like holy shit, I had to savestate through the entire game after level 3 and there's like 20 levels. The hypno disc race level is iirc the second to last level in the game and you can't beat it even WITH savestates. There's no time to even use them and even if you would you would lose that 0.01 seconds in reactiontime which is the marginal for error in that stage.
Had to use FCEU speedrun to get me past that level (watched it until he was through the level then stopped the speedrun and picked up where the speedrun left off).