what Thor is doing right now in Secret Empire is arguably worse than anything Emma has done.
The worst thing Emma did was help Mastermind mind control Jean Grey, because Jean later turned Dark Phoenix and destroyed a Sun (which killed an inhabited planet orbiting that sun). But she was indirectly responsible, her direct action was creating a device that allowed mastermind to create his illusions inside Jeans mind.
The second worst thing she did is what happened recently in Inhumans vs X Men. Destroying with Sentinels an aircraft full of inhumans, which seems very out of character in comparison to everything she ever did, even as a villain.
The third worst thing is killing Firestars pony
Thor right now is an Avenger of Hydra, a government that has destroyed Las Vegas killing over half a million people, and that has all of New York in a hellish demon dimension.
Villain is relative, because many Marvel heroes have done things worse than many villains. Black Bolt, Tony, Beast, Reed, blew up a planet in the last Secret War event. Beast has commited alien genocide. The same goes for Namor.
Basically, Marvel doesnt have heroes.