Melina Accepted Me, Though I Bear the Frenzied Flame

The story follows a Tarnished who has beaten Elden Ring. While researching Ranni's work, he accidentally discovers a way to enter a new world. By then, he has completed every side quest, defeated every main boss, and obtained every spell, incantation, weapon skill, and item. He can even combine them all to create new skills better suited to himself. He possesses every kind of power (basically, he's insanely powerful).