Man, I just finished reading 'Conquering System: Harem with Infinite Rebirths' last week, and honestly, the title lays it all out. It's exactly that—the protagonist, Xia Tian, dies in our world and wakes up in a cultivation universe bound to this 'Conquering System.' His power is infinite rebirth; every time he's killed, he restarts from a recent checkpoint, but with all his memories and a bit more strength.
The central tension is how he uses this to essentially brute-force his way through a harem conquest. He's not a typical overpowered hero; he fails constantly. He'll approach a love interest the wrong way, get murdered by a jealous rival or the woman herself, reload, and try a different tactic. The plot loops around these cycles of social and combat encounters. The actual 'conquering' feels less about battles and more about solving a complex, lethal dating sim through trial and error, which is a weirdly specific and kind of grim hook when you think about it too hard. I kept reading because I wanted to see if the system itself had an agenda, and yeah, by volume three that starts to pay off.