@GeneralVan: That's wrong, because Ichigo got weaker after the SS arc-
1. Zangetsu suppressed his shinigami powers to make him more hollow-like
2. He lost his resolve after the hollow showed up, and getting beaten by Yammy
3. The substitute badge suppressed his power
However yeah, YYH's Jin wins
One armed Grimmjow was holding his own against a hollowfied post vaizard training Ichigo while in base. With both arms he kills Kariya by boxing his face in Ippo style. Or grabbing him the throat and blasting him with a cero. It's like putting 100% Final Form Frieza against Imperfect Cell. Kariya is Frieza and Grimmjow is Cell. One may be in his most powerful while the other is at his weakest, but the latter will dominate. Anyone of the Espada would beat Kariya.