* AlwaysChaoticEvil: His villains. A common complaint about Ennis' works is the man is nearly unable to write villains that are not [[CompleteMonster Complete Monsters]] and are so horrible that it gets really boring fast from work to work. It comes off like he uses stock villains just to get his [[AuthorTract Author Tracts]] across to the reader.
* CrossesTheLineTwice: Ennis has an extraordinarily dark sense of humor and a penchant for sex jokes, which turns many would-be readers off from his work. While he's not unusual in that regard among other UK-based writers (Warren Ellis in particular can give him a run for his money), Ennis is the one who's built a reputation off of it.

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