Why is writing a Villain/Villainess story where the MC is actually an evil, unreasonable ass so hard? And why is this genre misrepresented by these bland as hell do-gooders?
You want Overlord. Though, to be honest, it would be a better series if Ainz was more villainous and had more character of his own, rather than having his minions do almost all of the villainy for him.
For a non crappy example that has better well...
damn near everything than Overlord, Hellsing Ultimate. Alucard is a villainous protagonist.
"The Executed Sage Who was Reincarnated as a Lich Started an All-Out War" is an 'ends justifies the means' villain, as his end goal is ultimately heroic. This series does Overlord better than Overlord did, with no messy isekai elements and an MC who actually has a personality.
For Villainesses, the one that immediately comes to mind is "The One Within the Villainess," but I doubt you'd like that, as she's more of an antivillain and is changed considerably by love/obsession.
There are more, you just have to look around and sift through things. There are considerably more villainous redemption stories than there are ones where the main character is just thoroughly, completely, and irredeemably evil.
As for this, this MC is just silly. She doesn't have the temperament for true villainy and we all know it, though she might cause quite a series of disasters with her overpowered magics. She just wants to do the oujou sama laugh that she's read about. Basically a chuunibyou, but one with real power.