The Male Lead Turned Dark After I Dumped Him [Quick Transmigration]

It's just a quick transmigration novel with a cheesy premise, old-school melodrama, and a Mary Sue protagonist. First of all, the protagonist is a quick transmigration mission-taker with the script in hand. His job is to cultivate the love interests in his mission worlds until they become the strongest people in their respective worlds. At the same time, he's a love cheat. He's also kind of naturally awful: the sort of scumbag whose heart breaks into several pieces, every one of them capable of falling in love. So after the protagonist uses the love interests and leaves, the worlds are bound to collapse, and the love interests have to go crazy and turn evil. You know what happens next: the protagonist gets sent back to cleanse the corruption of these different world-slice versions of the love interests. Since the tropes are all so cheesy, there have to be senior and junior brothers. The junior disciple who used to call him Senior Brother this and Senior Brother that, and climb into his bed every day on the excuse that no blanket was as warm as his Senior Brother, now scowls and pulls out a thick iron chain. Clang, clang, he locks the protagonist up in a dark room. We also need an ABO story: a lofty, aloof Omega adoptive father, so beautiful that his Alpha adopted son, a war god, can't help feeling stirred. But the love interest is a little insecure. After turning evil, he teams up with the protagonist's rival to make the protagonist a prisoner, then sneaks into his cell to mark him before the trial. So satisfying. We can't leave out martial arts and cultivation, either. The love interest is a beacon of righteousness, a mighty sword cultivator. The protagonist is the king of the demon realm, a powerful archfiend. They start out fighting and end up falling in love, with some melodrama thrown in. The wronged protagonist has to die first, and when he comes back to life, he finds the love interest has shattered his sword and gone demonic. He's carrying the protagonist around the mountains in a crystal coffin, shouting that the entire cultivation world should be buried with him! What a grand entrance! Finally, let's add a cute nonhuman character. The protagonist falls into the sea, and the love interest is a sparkling, silver-haired mermaid. At first they can't understand each other's language, and the love interest looks a little fierce, so the protagonist thinks he's going to eat him. Only later does he figure out that the love interest wants to have little mermaids with him. Hehe. Or the protagonist could fall into a mountain cave, where there's a long-haired, white-furred wolfdog, badly injured and unable to move. The protagonist comes every day to pet him. The wolfdog is furious, but can't fight back. Later, the protagonist nurses him back to health, and the wolfdog falls for him while being petted. He pretends to be reluctant as he tricks the protagonist, saying that in their wolfdog clan, only wives are allowed to pet them. From then on, the protagonist is his wife. Anyway, everyone knows the quick transmigration formula: make turning evil the main plot, then string together all kinds of cute tropes along the way for a fun, satisfying read! P.S. The original blurb's talent-show arc will be included too, so don't worry.