Khan had sparred on relatively even terms with Lord Mighty. Lord Enforcer believed his fellow Royal Guard would have won, but Khan still held his ground valiantly and forced Lord Envoy to intervene.
The Empire's Royal Guards weren't simple evolved warriors. They were the best of the bunch, having standards so high only four had seized the honor of protecting the Emperor.
Meanwhile, Miss Christen had evolved through the aided metamorphosis process. That didn't intrinsically imply weakness, especially after enough time passed, but Khan had always placed her under her fellow guards. Bruno and Adrian felt far stronger than her.
So, defeating Miss Christen could give Khan a good idea of where he stood. His existence ignored ordinary power classifications, but he wanted to have terms of comparison. If not for himself, he wanted his enemies to know them.