I want a story where a person returns to the past to defeat someone who they couldn’t before. I don’t want something where they are fixing their previous wrongs or something. Also they should not be super powerful before going back in time. After all, they died being unable to defeat the other person. I read a webtoon called Once Again My Life and I really liked the plot. A prosecutor is killed by a powerful corrupt politician and is sent back in time for the purpose of defeating him. The main character had a clear reason for being sent back in time. It was not a miserable person somehow got sent back in time and this time he will enjoy his life. It’d be interesting if the story was in modern times rather than being focused on martial arts.
Trascending the Nine Heavens. Only got to chapter 300 or so (still hadn't had his revenge, but had screwed up the guy a fair bit.)
I agree, Zhan Xian does technically fit your request. MC in the past became an immortal employed in the Emperor of the Immortal Realm's Army, dies, and ends up returning to his past. He immediately sets out to win all the fights he couldn't even really attempt to fight the first time around. Specifically, he wants to prevent a sect that taking over the Mortal World he is from, and he may want to get revenge for being tortured in the immortal realm by the sect's ancestor for "daring to fight/plot against his sect". Why do I say that the MC isn't trying to fix his mistakes of the past? Well, he didn't make any, not glaring ones, at least. He was just in a bad situation that was out of his control, and acted as best he could based on the knowledge he had. With future knowledge and an ability that could allow him to exploit a specific situation he had foreknowledge of (which is the basis of the story's name), the MC was able to change enough things in the past that things go the way he would prefer. Part of that is the MC becoming strong enough to basically fight off anyone that can be reasonably sent against him at any point in time.