When 7-9 East African monkeys circle around you whilst you are chained to a log spinning over a bonfire, as they all do best mates from fortnite and slap your face with their balls one by one.
Great Explosion Murder God Dynamight refers to someone who is better than you, me, and especially Deku. It also can refer to someone who has a massive crush on Kirishima.
Person 1: Woah, no way, Great Explosion Murder God Dynamight is so amazing!
Kirishima: Yeah, I know, that's my husband who's still too embarrassed to tell me he likes me :)
Great Explosion Murder God Dynamight: *Barks*