I recently rewatch the Grimm series and acident with the blindig wesen and crashel mortel make me think that Grimms are most powerfull being. My theory is whenewer grimm encounter something new and danger he "Evolve" like with superhearing or with slower metabolism and suspended animation (zombie mode). Because how could grimm kill hexenbiest is its so powerfull and cul kill him with swing of hand and then what if when grimm will be for long lime confront with hexenbest power make him immune to that. and what if Nick dont get from Musa power couse juliette but because his grimm body evolve and he become imune. When hi fight akimu kimura (sorry i dont remeber name of coin hunting wesen) he got beaten and suddenly he stand and easily overpower him - Evolve.