Grindelwald didn't lead a charge of pure-blood supremacists to kill a teenage boy, his friends, and take over the wizarding world

Can't talk never watched Fantastic Beasts

Actually never watched the full Harry Potter series but I've read the books six times now

Shooooot I read the question wrong.

Fairly sure Voldemort had more followers and killed/had death eaters kill a lot more people but don’t fact check me on that.

Grindlewald manipulated Credence by saying that Dumbledore (both) had abandoned him. And also the Chillin, he killed it to become leader and take over the world. He wanted to kill all the muggles or no-mags. Voldemort was just obsessed with killed Harry.