Sometimes you can't beat a good bastard in a story, someone who will do underhanded tactics to win, kick a defeated opponent when they are down or is always about the reward after they complete a quest/job.
Been reading The Greatest Estate Developer and it's your standard Isekai tale, guy wakes up in the body of a lords eldest son he read a fictional story about and knows they are in massive debt, all die to be the catalyst for the knight that serves them who's the MC. So he uses his architectural knowledge to change their fortunes but does it in the most bastard way.
He'll bitch slap an entire college full of stuck up nobles because he can get away with it, kurbstomp his opponent after he wins a duel to then trick him into exile, force a water contract on a rival noble that essentially binds his future generations to pay him extortionate fees and much more. This series jusy passed 100 episodes and has some of the best faces I've seen from a series.
So whether it's Leon from MobuSeka or Amos from The Expanse, who's your favourite fictional bastards?
Rance, hands down. Uses his party members as meat shields, sends people on suicide missions or as hostages, pushes allies off cliffs, sneak attacks bosses, lies in order to sleep with women, rapes women while they're tied up instead of rescuing them, personally tortures people in order to gain information, abuses his authority whenever he gets to a position of power, uses voice changers and blindfolds to cuck other men, kills people that get in his way or looked at him funny, publicly rapes women in order to humiliate their allies, among other heinous acts.
On the good side, he literally saves the world, he's always there to protect his women, he kills rapists, child abusers, gays, and uglies, he's ripped with Olympic-tier athletic abilities, he pulls the women around him out of depression, he likes to preserve the innocence of young girls, and he's also surprisingly delicate when dealing with abused women.
These lists are not exhaustive, with more than 30 years of history he's had a long career. I once read a rumor that said that popularity polls in adult game mags had to be changed to exclude male characters because he would win 1st place every time otherwise.