By feats related to environmental manipulation, I'd say Kyp; his freighter feat is as good as Galen's showings, and his black hole feat is beyond anything Marek has done.
By feats related to combat, you could argue Galen given his army-busting and matching Vader, but Kyp hasn't necessarily been in the same situations to allow for that comparison, I dunno. Kyp does underperform at times.
By powerscaling, accolades and implications, Kyp Durron definitely; he's been suggested to have raw power on Luke's tier, while Galen is distinctly below Sidious.
Overall I'd say Kyp wins Force and all-out if he doesn't job, sabers is murkier.