Что случилось с Грохом из Гарри Поттера после битвы за Хогвартс?

Не умер.
Grawp is the only giant fighting on the good wizards' side in the Battle of Hogwarts, probably in an attempt to protect Hagrid, as he frequently calls his name while fighting the giants on the Death Eaters' side. Grawp participates in the victory celebration over Voldemort's defeat (albeit from a window, since he is too big to fit into the hall), and the Hogwarts students show their appreciation by tossing food into his laughing mouth.