The thing is ainz was always a villain,this is not a story about someone falling into the dark side,the moment ainz entered into this world he was an undead that didn't care about killing,ainz from season 1 is the same ainz we see here in season 3
He's not the same Ainz but you never see the change in the anime. In the novels he actually points out how his mindset has been changing more and more the more time he's spent in that undead body to the point he starts losing the value of human life and anyone beyond Nazarick. In the novel it's the devolution of a typical human into an undead being that is willing to massacre millions.
he notes his inhumanity, his willingness to commit murder, his lack of regard of any kind for outsiders, and his indifference to gore all in ep 3. His change isn't recent
Here's the thing though, if they were humans in a world of monsters Ainz would be deemed a hero or at the very least just a (neutral) guy who the monsters should just leave the f alone. goblins invaded the "castle" because they wanted food/supplies? Kill them all, who cares, so what if the goblin kids lost their goblin parents. Humans invade the tomb of monster for treasure? Man, they didn't have to kill them all, they had families.
Ya know, Ainz' alignment sits at "Extreme Evil" with a Sense of Justice of - 500 ;) Even among his subordinates, the only ones reaching the same alignment and Sense of Justice are Demiurge and Albedo, with a couple of others at least coming close to that level of evilness. So, amongst that den of evil monsters, the most evil one of them all is, in fact, Ainz, along with Demiurge and Albedo. In case you didn't realize, Ainz himself is not above experimenting the same way that Demiurge does (keeping Roberdyck alive to test what happens to his powers if the god he believes in is replaced is not much different from Demiurge's human experiments at his infamous ranch where he breeds those abelion sheep). So duh, Ainz is a bad MF...
The members of the guild Ainz Ooul Gown were roleplaying as a villainous guild, the first condition to join was you must be an heteromorphic race which very were being targeted for not being a humanoid race so they banded together and became one of the top 10 guild on their server! Edit: changed anthropomorph into Heteromorph! Anthropomorph means animal like
I dunno if the episode ever said, but Demiurge's command doesn't work on or has a lesser effect on people over level 50, and more so if they have a strong will. Or at least so says his Wiki. So that means the Emperor would have to have a stronger will or be around level 50 to not submit to the command