While Grimm initially gives the impression of being a fantasy series that follows the usual trope of the chosen one who has to best the creatures of the night, it slightly subverts that in the first season. The difference is only small, but important enough to make the show fun to watch, as you can never be sure what happens next. Granted, that only applies to the meta-arc of the first season, as it’s a typical monster-of-the-week formula on the episode level.
Grimms are humans who can see the monsters among us, have hunted them for ages and are feared by them. The Grim of the show though, Nick Burkhardt, is first and foremost a cop and a Grimm second. Instead of murdering the monsters wherever he sees them, he only acts when they harm others. One of his best new friends is a sort-of-werewolf called Blutbaden (like all the monster titles on the show, it’s horribly mangled German).
That’s not to say that all of the monster are actually just fantasy creatures that want to get by, most of them are deadly in one or more ways. Sometimes their deadly nature is part of who they are, sometimes they really are monsters inside and outside. But that Nick manages to discriminate between those cases, going for the murderers, helping those in need, whether human or monster, and showing mercy whenever someone really can’t help himself, sets his character apart from similar ones on other shows (and others Grimm probably as well).