Apologies if someone else has suggested this before. I'm not going to read enough comments to find out. But why doesn't Harry just say in Parseltongue, "If you let me conquer the world, you will be more happy, and have more fun." Harry can totally deliver with his transhumanist future by uplifting normal people so they aren't "idiots" that bore Voldemort, and giving him the kind of rivals he wants to fight with. Like, worst case he has to leave a planet or whatever of shitty conditions where Voldemort personally fucks people up, because that's the only thing that will satisfy him. But it's still worth it for the improved chance to get the rest of the universe.