IMHO the Warhawk trophies are the hardest to get. Virtually every PS3 game has *some* trophies that will be difficult and require a great deal of persistence to get, but few run over the 100-hour mark.
Warhawk not only has some that require a great deal of persistence, but they also require you to be indisputably the best player at some point in a multiplayer game and enjoy a fair amount of dumb luck to pull some of them off. Warhawk's trophies aren't measured in hours or tens-of-hours, but rather hundreds-of-hours of play.
I looked at the list when the trophy-support was added via patch and immediately wrote off half of them as being virtually impossible for me to obtain, because I simply don't have that much free time to invest in one game.
