Tekken 3
That game is still one of the best fighting games ever made, but I never managed to unlock Dr. Boskonovitch because you have to beat the survival mode FOUR FUCKING TIMES!!
Holy shit, I didn't even complete it once, because most of the times you can't see your enemies and they're kicking you from out of the screen but you cannot just stand back and wait for them to come closer NO, because the time runs out so ridiculously fast and you just have to go to the corner of the screen and spam some attacks and suddenly there are more of them and you can't even react to them using you as their punching bag.. And if you managed to pass those bastards you have only like 14 seconds left to kill yoshimitsu or kuma with only a third of your hp...
That game really made me rage like nothing else, because you have no possible chance to beat that..