Originally posted by carthage
Nothing.He could barely defeat trainee Bane.
But he should probably be a match for another guy who got beaten by a non force sensitive i,e Malak.
Kas'im mastered all seven forms of lightsaber combat and spent decades perfecting them. This in and of itself marks him as an extremely skilled duelist.
While Kas'im being possibly the greatest swordsman ever may have been Bane's opinion, it's important to remember something about Bane. Bane is the guy who spent hours upon hours reading about the ancient Lords of the Sith in the archives, which include the likes of Kun and Hord amongst them. Bane also hates the Brotherhood. The fact that he considers that Kas'im could possibly be greater than these ancient masters of the lightsaber that Bane holds in such high esteem is very impressive.
Kas'im also fought with a striking speed approaching Grievous's max.
So yes, he is very impressive.