Hmm not sure which one i'd say on one hand there's
Ultimate Marvel vs Capcom 3 on PS3 (those trials are just ugh)
Then there's also stuff like Deception 4 The Nightmare Princess
I was among one of the first few to actually plat this game and since i made videos on each quest my vids are basically the entire guide for this game so others can plat it aswell.
As for max grindy one i'd pick FEAR2 and honestly i don't think i could ever plat that again.
If anyone else wants to look at my plats and decide one for me here you go:
https://psnprofiles.com/Tosmasta00/log?order=rarity&type=platinum&dir=asc