I platinum every game I play on my PS3, even the stuff I end up hating. Thankfully, either by luck or the fact that I can usually trust my hunches, there haven't been too many games for the system that I ended up destesting.
However...
There will always be Duke Nukem Forever. Fuck that game. The mere fact that on every difficulty level you have to cower like a little bitch because the Duke can't take a couple of bullets without having a near-death experience is bad enough, but on Insane mode? Eugh, all the games faults really shine through there. I got the platinum as fast as I could (a week) in the vain hope that I could sell it for a decent bit of money while it's reputation for being a shitfest wasn't widely known.
inFamous is another. Got it for free in the Welcome Back package. The more you get shot, the harder it is to make out what's going on. Constantly getting shot at in an open world that begs for you to be left alone so you can explore a bit. Wholly loathesome characters. Repetitive missions. Surprisingly poor graphics for a game that came out in 2009. Oh yeah, you better believe that second playthrough was pure torture.
Other than that though, going for trophies has been a mostly pleasurable experience!
Edit - Poster above me mentioned FFXII. I'm inclined to agree with that one. Not quite sure how I got to end of the world's most uneventful RPG, but I did somehow.