The most difficult part for me in the game was trying to get 100% completion, obtaining the Lady Luck dress sphere (which to this day, I've never succeed in kicking Shinra's ass), finishing the Fiend colony (never got to fight King Vermin), and of course, the Via Infinito. Aside from all that, I thought X-2 was an enjoyable entry and loads of fun but I still like X a bit better.