Tagami Tatsuya has an ambition of world conquest and the first step of his plan is to make every one of his female classmates pregnant.

Which anime villains would be hailed as heroes in another anime?

Off the top of my head, the Green Clan in K: Return of Kings.
While they cause a lot of chaos, the idea of giving everyone powers so that there is monopoly of supernatural skills along with the very flexible idology that focus on the personal freedom and independence of its members make this clan very appealing.
The fact Hisui and co.
form something of a family, complete with lazying about playing games and shooting debris as opposed to being on ‘villain’ mode all the time adds a weird affectionate feeling to it all.
Their headquarters is a room that could be in any normal family home. The lack of an actual hierarchy, that is perfectly in line with Hisui’s notions of equality contrast starkly with the borderline cultish behavior of both Red and Blue clans.
Unlike these, Hisui does not view defecting from a clan to join another to be treason or even wrong. Of course, the Green clan does not qite view rank and file members as actual clansmen in the proper sense but they are free to leave at any time. Come to think of it, the Green clan is closest in structure- or lack thereof- to Shiro’s Silver clan.
This may explain while Jungle is the villain, it still comes across as very likable.
Its members form a tight unit of a few people as opposed to being a big, highly hierachical pyramid-like structure as the Red and Blue are. Jungle is more attractive, to me at least, because of its playful nature.
Virtually everything in Jungle is based on playing and having fun.
There is more at stake but this happy go lucky attitude is something heroes usually display. Then there is Hisui himself.
It is difficult not to sympathize with the Green king.
He is intelligent, has a love for life that is overwhelming and went through hell.
He tries to negotiate with everyone in order to reach a non-violent solution whenever possible (unlike Red and Blue) and is affable, understanding of his mates’ quirks and respectful of their personalities. He does not demand loyalty either.
With a few changes, Jungle could easily have been the good guys in another show.
Hisui is probably overall nicer than Lelouch, for example, who despite CG’s not entirely black and white morality, is the hero.