Myself since I'm complete piece of shit.
However, my stepmother would definietly be a close second. She was abusive towards my dad (physically and verbally), started a whole bunch of drama within my family but had the audacity to play victim, physically attacked my mom, threw my brother on two occassions and also threw stuff at him on one occassion (she has stop hitting him and doing anything physically to him years ago, but that's because that would risk her getting in trouble which would lead to the government finding out she's here illegally and deporting her), was manipulative, loud, and was overall a scary and uncomfortable person to be around. My friend who lived in the same buliding even admitted to finding her scary, which I don't blame her for.