I Cultivated A Nemesis is a Manga/Manhwa/Manhua in english language, Action series, english chapters have been translated and you can read them here. You are reading chapters on www.mgeko.cc fastest updating comic site. The Summary is

The demon king possesses a return ability, but is continuously killed by his nemesis, finally, he chooses to return, but then becomes the older brother of his nemesis. He decides to use his abilities and raise his nemesis to become useless, but this began to go in an unexpected direction