Dreaded parts in games.

[Arjahn]

Bosses that you're supposed to lose against, when done poorly, that is.
A good example of how to do these right is at the beginning of Paper Mario (64) where you fight Bowser right out of the get go and he shows off how powerful he is with his new Star Rod, and you can't even touch him, then he punches you out of a window. The entire battle isn't just a cutscene where it shows you getting your ass kicked, you as the player actually feel sort of helpless as your attacks do nothing and he deals major damage to you, he being Bowser, the guy who you've been destroying for years in other Mario games. Not to quote Egoraptor here, but just like in Mega Man X, this first battle serves as a driving force throughought the game, you're not just beating levels to save a princess from some evil lizard/dragon/turtle thing, you're becoming stronger so that you can find Bowser and get some revenge.

That's how you do these well, 98% of other games who try this end up making you fight a guy who's really strong, so you waste all of your items on trying to defeat him, only to realize at the end that you were never supposed to win and let him kick your ass.

I'm looking at you Tales of Symphonia.