Trying to go back through Medal of Honor: Allied Assault on Hard and reaching the Sniper Town. Sniper Town was already one of the hardest levels I've ever played, and even on Easy it was incredibly difficult, and not really in a good way. Hard mode is something only for masochists. Surprisingly, though, the Hard difficulty made a few other areas harder than it was, especially the manor house right before it.
There was also Tales of the Abyss when you have to fight Arietta, Legretta, and Largo all at the same time. Each of those bosses were a pain to face individually. I didn't even want to know what they would be like together. Sure enough, I hated the boss fight. It isn't even that challenging. It's just really annoying.
Finally, there was any time I had to do the Mako section in ME1. Once I saw that piece of a crap waiting to be used I instantly knew I was in for 10-15 minutes of an absolutely horrible vehicle section. Worse is that it would take even longer if the horrible controls led to my death and I had forgotten to save at a decent point because ME1's save system was terrible.