I've been watching two animes recently. Both have similar main characters, in that they have a past where the murdered many people and now live a peaceful life. They are both pretty old but I watch them on a tv channel like streaming service.
The one I know best, Ruroni Kenshin, just "started" a new arc where the main character has to confront that his past is catching up with him. An old rival is out for his life, and he is as good as ever, while the main character has taken up a life of peace and hasn't fought rugged in a long time. He wonders if he is capable for the task.