The Regressed Demon Lord is Kind

My whole life, all I wanted was power. I churned the world into rivers of blood and eventually gained the title, "Demon Lord of Strength". However, all this became useless when I lost to a party of heroes. But what can a loser say? As I laid dying, I was forced to listen to the hero's gibberish: "If you are born again, I hope that you will live a kind life!" But huh? When I opened my eyes again, I was back in the past. "What do I have to do to live a kind life?" This is the beginning of an ex-Demon Lord’s journey to live a kind life.