|“||I wanna make the insufferable suffer! Bring back the dark! Bring back the gruesome! Bring on the Grimm!||„|
|~ Grimm's declaration|
Grimm is an outright villain who despises all things that are traditionally seen as cute or nice, to the point of wishing to obliterate them from existence - which he seems to be able to do with his mere presence, which warps not only the world around himself but people and animals, making everywhere Grimm goes become a kind of Hell on Earth. He also expresses a bitter and sardonic attitude towards the worlds and their inhabitants. However, he is shown to be weakened by water or any other kind of fluid (including vomit) which will cause him to drown.Nevertheless, Grimm also seems to have a sense of justice when it comes to stories. Many fairytale protagonists are characters he feels are undeserving of their good fortunes, reinventing the tales as a way of punishing them. He also greatly believes that victimized leads, such as Cinderella, should have their chance at taking revenge on their abusers and partakes in corrupting their tales in order to give them that chance. However, his desire for utter destruction and references to "wanting to give retribution" to a murdered outlaw in a western comic book of his series calls this into question as to whether or not Grimm truly believes in an "eye for eye" mentality or if he just uses it as justification for his horrid actions.
Despite this, Grimm himself is quite the aggressor and murderer, often taking pleasure in causing harm, especially to children. In addition to his sadism, he also sometimes demonstrates a level of masochism, such as egging on an angry god to strike him. There's also an irony in that while Grimm allegedly hates Karma Houdinis, he himself is one, having wrecked these worlds and escaped practically unscathed.
He also has starred in a limited comic series wherein he enters a world based off a comic medium (such as superhero works) and corrupts it to his liking, being arguably worse than his game counterpart. He begins with "Crisis on Earth 57" where he empowers the supervillains to violently murder the superheroes, all because he is disgusted by "good's triumph over evil". In "Gotta Kill 'Em All", he corrupts a Pokemon-based world due to his understanding that such creatures with elemental powers should lead to utter chaos. He even goes as low to corrupt worlds based on Bone and romance comics to fit his liking, the former ending with the heroes killed by a dragon-like beast and the latter ending with him corrupting the woman to become a man-eating beast.