My latest hight difficulty achievement was getting Platinum trophy on Metal gear Rising.
Yeah I looked at the trophy list on PSN profiles and it looks pretty intense - props to you!
Personally I can think of two achievements that were pretty difficult for me: getting a ten star rank in Silent Hill 2 and/or getting a black 5 star trainer card in Pokemon HeartGold Version. I must have put in 500 total hours into that game, and that majority of it was just to compete that Pokedex. Guess that may be why I've lost my taste for Pokemon since then