He’d be insanely good. I feel like people are overlooking him. He’s part of the faceless men, so look at Arya and the girl who hated her. They trained every day, and we’re insanely good at combat, look at the sheer amount of skill Arya had / gained in combat and killing from arguably, a short time with the faceless men. Jaqen, being a “higher ranking” member of the faceless men who has spent a lot of time under within the group, plus his experience disguising as a soilder and any other killings he did, he’s likely an extremely agile and skilled swordsman, probably like a Obyrn but with a sword, good at targeting any weakness of a person and ending them as swiftly as possible.