Once Vader learned he had children, he did everything in his power to protect them despite cutting off Luke’s arm. He genuinely loved them and couldn’t see them suffer.

Same with Garmadon. He did everything he could to protect/avoid fighting Lloyd.

Who would vote Darth Vader?

To be fair, Vader cuts Luke's hand off in a duel and forces Leia to watch Alderaan get destroyed, plus he chokes Padmé almost to death while she was still pregnant with the twins. He is far from a perfect dad, redemption or not.

No one is a worse father than Ego. He murdered thousands upon thousands of his own children just because they did not inherit the Celestial gene.

Worst as in most evil, or the one I like that least?

Ego, easily. Having a father who killed your mother should probably make the other options look like nothing in comparison.

Too easy.

I voted Crimson because I thought the question was who had the worst writing

Ego is the worst father without question

You made it obvious the moment you put Ego on your poll.