It is a fantastic Korean movie to watch from start to end.
Monstrum is like All of Us Are Dead in that a monster manifests out of nowhere, only in a rural area, and kills indiscriminately like no tomorrow. Also, it devours it's human prey and leaves mutilated body parts all over the place and fair share of gore in its wake which is not too dissimilar to the not so smart zombies.
Something else they have in common is the battle for survival and a group of people having to deal with it that are directly impacted by it.
One difference is All Of Us Are Dead is based in modern times whereas Monstrum isn't, also, one is a tv series and the other other one isn't.
NOTE: I was here to recommend Duty After School and Sweet Home, but seems I am left with Monstrum.
I would recommend all three.
