Gamethrowing. There could have been a miscommunication....You can't out your partner because you're mad they did something. Regret should have reported Han for possibly gamethrowing by voting different than him, not outting him allowing town to have an easy win.
I would like a second-opinion on this one. His maf partner clearly screwed up, but I don't think it was enough for him to justify outting his partner and giving up on the game. I would think to make it fair just give neither of them a violation to balance it out.