He was capable of outskilling one of Koro Zill's battlemasters in H2H, killed multiple nexus amped Sith sabers on Dromund Kaas, and was outfighting Gavar Khai a renowned Lost tribe Sith saber, as well as stalemated Vestara Khai and killed Nighsisters iirc
He doesn't have many force feats, but his showings with a blade are better than. Kas'ims.
Trolling aside, tbh none of those enemies really have any notable feats or accolades of their own. Ben's beaten a no-name "battlemaster", beaten sith sabers who are analogous to jedi knights, and then Gavar Khai who isn't even a Sith Lord. At least Kas'im was considered the best swordsmen in an entire sith order, sure they were weaklings but were probably superior to no-name sith sabers.
I guess Ben does kill (amped) rancors with a lot greater ease than Kas'im did though.