Buggy and Yonkos injuries only lasted within their respective one single arc each.
While Mihawk's injury lasted for 2 arcs, from Baratie to Arlong Park. Further evident with the fact that its the one injury that gave Zoro a permanent scar.
Kuma's damage lasted for 2 arcs too (Thriller Bark to Sabaody) but it didn't hinder Zoro much from going out to fight the Pacifista and was resolved pretty quickly later on, compared to Mihawk's slash that flat out stopped him from fighting Arlong right after beating Hachi...
I pick Mihawk here, with Kuma as close second. The rest is irrelevant (wish the Hakai had proper consequences and not magically healed within 1 week... oh well.)