Buta Kizoku wa Mirai wo Kiri Hiraku you desu - Vol. 2 Ch. 6 - The first step.

[Vincentius]

absolute peak! A man who can not only apologise but do so in front of a crowd is a man who deserves respect. So long as his redemption still takes time this may become one of if not the not the best villainous noble story in a while.

(Sorry for dragging this back up; I forgot all about this series from lack of updates and am rereading it now.)
The best part is that he, strictly speaking, didn't have to. He was fully within his right as the victor of the duel to just go about his business and quietly become a better person.

Instead, he took the opportunity to apologize for all his misdeeds in front of a large audience; and he not only lowered his head, but also kneeled to do so. Considering the whole catalyst for the duel was his incredibly huge noble pride, that speaks just as loud, if not louder, than his words.