Palpatine and Runeard, why?

THEY BOTH ARE TYRANTS!!!!!

In terms of BEING a parent? Easily Shou Tucker. How anyone can be THAT awful to their kid is beyond me; he trapped her in a fate worse than death. At least those other parents just at worst tried to get their kid killed (and some of said parents didn't even do that). He is easily one of the worst parents in the entirety of fiction.

Gozaburo Kaiba! He’s Abusive, a Plagiarist, Sadist, an Arms Dealer , and just downright cruel!

For me is Ozai because he was an abusive father to Zuko, when Zuko refuse to fight him he burn half of his face to punish him and even exile him.

All of them.

Shou Tucker.

Shou tucker is the worst parent, due to his experiment with alchemy with his daughter and his pet, in order to gain credibility

Mother Gothel.