THIS IS BAD ASS!!! I am also detecting an element of Flying Monkeys in his expression which is making it even more bad ass. Though that's probably the taste of the demon's blood broth he's having with his sushi. I love this chunky painting style.
Its so nice to see Grom with a genuine smile of happiness on his face amidst war and struggle. Its so sad he died in battle, but at least his sacrifice freed himself and all his brothers from their curse.