Actually this year so far probably the lats and chest, last year would be the chest and tris. Before I got hurt in April I would have said quads/hams/glutes but now they have gone to shit lol.
I would have to say tris and lower back(although I pulled a muscle in it it's ALOT stronger now that i'm fully recouped).
I would also say that my lats have gotten weaker and for some reason squat has stayed the same and deads have gone up. ( I need to focus more on the squat).