I don't have the platinum but I would say Lost Planet 2 since it requires you to hold a WR for a trophy and it's been such a long time that many of the WRs are pushed to their limits. I've never played the game and I don't know that much about it but from what I understand it could easily be the hardest.
did u get plat on that game? I don't even think it's possible to get platinum anymore, especially for online
No i didn't i just got around 30% of the trophies
I think only way to get the plat for killzone 2 is on a trophie service.
It is a shame because it is a great game.
I recently got myself Yakuza Zero while on holiday. When playing it for the first time, I noticed it was in Chinese instead of Japanese, so this will be the hardest for me (I didn't know they had them Chinese subbed..)