Random!
Kenshin seems to reserve his punches for the people he's actually concerned about (see examples: Sanosuke and Enishi). He drops his sword and uses his fist when he really wants to drive a point home and he's already maxed out in frustration.
Kenshin likes to make flowery speeches full of reproval and disappointment. And he actually gets away with it. Saitou makes pointed remarks about this several times.
The one who best understands Kenshin's enemies is...Kenshin.
Saitou doesn't acknowledge Kenshin as Kenshin until the 25th volume. Before that, he always referred to him as "Battousai." Until he finally realized that Kenshin was not a killer at heart, and backed off on his "Aku soku zan" plans for Kenshin.
Kenshin is surprisingly prudish. He has major issues with Misao's outfit.
Kenshin has no problems showing the "Battousai eye" to jerks and idiots as an intimidation tactic. He even gave Saitou the "Battousai eye" when Saitou made a remark about Kaoru just before Kenshin left for Kyoto.
Raijuuta -- the guy who maimed his own student -- holds the dubious honor of being the only villain Kenshin truly despised and disdained. This is sort of funny, because Kenshin treated him -- in the end -- like cannon fodder, and Kenshin rarely treated even cannon fodder as cannon fodder. Most of the time Kenshin just goes "That's bad, don't do it again, okay?" In Raijuuta's case, he's "Just shut up and take this beating, okay?"