Gigantamax Jirachi is a Gigantic Jirachi, appearance of the "common" Jirachi.
She seems pretty cute and kind but can be naughty in various ways- she may play around with tinies as a type of entertainment, maybe destroy some giant or large buildings just for fun or just straight up start a feasting rampage.
Research
Research regarding her is quite interesting.
She seems to have an ability to change her height at will- unsure if it is her wishes or some mythical property only she has.
She also seems to enjoy tiny creatures as a meal or for them to worship her giant height. So far she has a few very loyal cuties: A Cute Fluffy Foxxo, A Cute Fluffy Protogen, A Cute Little Fluffy Imp and A Cute Pancham.
Artist OrezSuke