Audience-Alienating Premise: The premise of this series involves a socially awkward otaku teleported into a fantasy world as his video game character (a demon king) and two girls ended up becoming his slaves by mere accident with fetishzation of slave girls will turn off a lot of people.
Keera L. Greenwood is the older brother of Shera and the prince of the Kingdom of Greenwood. He is known to be physically abusive towards Shera, while seeing her as nothing but a Sex Slave that he rightfully owns and can use to continue their bloodline. Eventually, Shera had enough of his mistreatment and ran away, leading to him obsessively trying to recapture her and bring her back. He has a complete disregard for life, not caring how many people he endangers to achieve his goals and believes the entire world exists to please him. This is shown when he callously declares war over the pettiest of reasons, or when he summons the Force Hydra (a dangerous and destructive beast) even though he had no means of controlling it. He's also shown to be incredibly racist to all races other than the Elves. When he finally recaptures Shera, he has her chained up and attempts to rape her while also putting her under mind control magic to make her desire to come back with him.
PaladinSaddler of the Church of Celestials is a twisted sadist behind a mask of pleasantry, Saddler butchers villages he suspects are "evil", killing them to the last man, woman and child. A torture enthusiast, Saddler is fond of attacking demihumans or anyone he so much as suspects of worshipping demons regardless of logic or justification, taking them and torturing them to death as a form of "purification" and justifying his beliefs under the notion that he is a god. When he captures Diablo's friend Rem, Saddler tries to torture her to death as well, his supposed righteousness nothing more than a mask for the twisted monster he truly is.
Does Not Like Men: On a meta-level, the author. Through 9 volumes of the light novels, every single one of Diablo's major allies is female (or identifies as such); while aside from Diablo himself almost every named male character has been some kind of antagonist, one of the rare exceptions being an annoying Chivalrous Pervert. It gets so bad that twists such as a certain party member turning out to be a Sweet Polly Oliver or the recent inheritor of the Swordmaster title turning out to be a young woman come as no surprise at all.
Escapist Character: Diablo. Even more so than the usual Isekai protagonists, playing straight into the fantasies of players becoming their video game character and an extremely overpowered one at that. He also delves deeper than the usual Harem Genre wish fulfillment as Diablo has no qualms on getting intimate with them.
Funny Moments: Diablo shows even demons can get drunk and also sees cute bunny girls as pillows.
Memetic Molester: Diablo. Little surprise he became one given the Audience-Alienating Premise of a 30 something otaku who acquired two teenage girls as his slaves who he has groped on several occasions. He also shared a kiss with a technically newborn girl.
If kidnapping Shera and trying to molest her wasn't enough for Keera to cross it, summoning the Force Hydra to incite a rampage (without any remorse for those he endangers) surely put him in irredeemable territory.
Galford crosses it when he decapitates Keera.
The Woobie: Some of the cast have tragic backgrounds.
Rem being born with a curse with Krebskulm sealed inside her, she keeps it a secret to avoid being alienated and the Fallen are after her to release the demon lord within her.
Shera runs away from her kingdom, due to being abused by her older brother.
Diablo, when he was Takuma Sakamoto, is used and manipulated by others who pretend to be his friends in his childhood.