Hmmm, let me think... Ever read "I've become a villain that hero is obsessed with"? I really like that one, just have to stop procrastinating from finishing it.
It's about a guy who transmigrates into his favourite comic book 'Stardust' about a superheroine with that same name. He really likes her, but it's basically a tragic story where the world gets destroyed in the end, so he intends to change that. She's the type to grow stronger in desperate situations, so he becomes her villain archnemesis to make her stronger. Funnily enough, since even with plenty of property damage he never kills civilians and only villains, people actually call him out on his livestreams: "Are you sure you are a villian? With villains like you we don't need superheroes!"
Then comes the romance aspect, as this is definitely a harem. MC really likes Stardust, but he is more like a devoted fan so while he pushes and encourages her to grow stronger and publically supports her, he doesn't exactly aim for her heart. And his team of supervillainesses is growing over time, with many of them falling for him before Stardust does. But to me it's kinda funny how she slowly falls for him and then has to fight with MC's fans on the internet to debate who he is better to be shipped with.
It now has a manhwa too with around 26-27 chapters and I think it's a very good one. Better than this one's adaptation, definitely.

Well, at least for now. This guy isn't going for the Solo Leveling thing where only he gets stronger, but instead is the nurturer-type that likes to make other people stronger. I prefer these kind of stories where the MC knows how to do OP builds and helps others get to those.