The Zombie Knight by George M. Frost

MC starts off depressed and with low self esteem but he ends up gaining a lot of confidence and motivation to live. The author does a very good job of connecting his power growth with his change in mindset and resolution of previous issues. A lot of “character development” novels just have a shitty MC who suddenly becomes a charismatic gigachad and all of his issues vanish when he gets strong enough or they have an endless slog of whining and therapy from side characters. In this, he doesn’t have his issues magically fixed but he does learn to live with them and outside of some conversations with the reaper and eventually his mother he doesn’t wallow in them. If you are looking for an arrogant and ruthless CN type of MC, he will never become that, but I do think he is ultimately a likable and interesting MC.