There's the fact that despite his age, Gin is extremely skileld in hand to hand, not only in katanas but with naginatas, kunai, senbon and explosives, a natural at finding at analyzing battle skills and patterns, finding weaknesses and abusing whatever in the enviroment can be abused or creating plans in seconds.
This all without accouting for the fact that he can fight Utsuro, skillful enough as to fodderize nearly the entire Shinsengumi without any eyesight and fighting Kamui. Kamui is recognized as one of the straight strongest of the Yato, a race of human-like Amantos (Aliens) among the most powerful, being said an army couldn't compare to 4 of them, a battle and killing instinct making them seek the strongest of fighters in the universe even if it's one of their own, with inhate battle instics, skill, flexibility, adaptability, skill, yadda yadda yadda far above humans. So Kamui is pretty much far above a normal Yato, alongside his father Umibozo who is considered the best hunter of the universe and Housou who's called "King of the Yato". Both Umibozo and Kamui were among the people that fought Utsuro, and he could still match and defeat them. He had even barely regenerated his eyes when he blocked a kick from the back from Kamui without looking.