Basically Pan, Cora and George are the worst.

HORRIBLE! Terrible father and terrible character!

I think Baelfire's mother, Milah, was the worst parent of them all. She just gave up and abandoned her child because she "changed her mind". Despicable.

They were all pretty bad parents at some point, honestly, but at least Regina and Rumple tried. I suppose in her own way, Cora did too.. and George did love James, even if he cared nothing for David. So, of these options, Pan for sure.

like DUH!
Cora too though.

Or King George. Then Rumpel & Cora though i'm pretty sure they loved their kids despite their wrong actions. Regina well, it's not in my list with the worst parents.

Of course. Peter Pan didn't love his child at all, he was actually going to kill him at one point. At least the others, despite being quite bad parents, loved their children. Second I'd pick Rumple, purely because of the past and then lying on his grave, saying that he'd change for him and clearly he hasn't.

I agree with anaswill. Every parent proved they somewhat cared and they trie- and Cora it kind of wasn't her fault but Pan is the worst parent ever! He never loved Rumple. He never tried. He was ungrateful for Rumple so yeah...

^ Which makes me wonder why the hell people love Pan so much.

Pan was a terrible parent but he never really, actively hurt his son, he just didn't love Rumple.
Rumple loved Baelfire and never hurt him, he just loved power (and the courage the power gave him) more.
King George was never really a father, or, if he was, he was James's father, never David's. When his son died and he got a substitute for the kingdom, there was no point in loving a stranger who happens to be your son's twin.
Regina made mistakes with Henry mostly because she had a terrible mother of her own, and because she tried to control him too much, to the point where she stifled him, but she loved him and she proved it by changing for him.
Cora... Cora was a monster. She not only didn't care, she actively tried to break her daughter's spirit, killed his True Love and forced her into a marriage she din't want. She singlehandedly broke her daughter's life beyond repair, and then just stood there smiling while she cried.

^ Also let's not forget Zelena. She abandoned her new born child and never looked back.
Oh yeah Cora is the worst parent among these!!!

1. She messed up two children's lives in opposite ways - what an achievement.
2. She abandoned a new-born in the woods to die. At least Pan waited until Rumplestilskin was old enough to survive, and he had those weavers to take care of him. And she defended her actions in being what was best for her, in direct contrast to the concept of giving up a child to give that child his/her best start.
3. She abused Regina with magic, killed Daniel in front of her after pretending to give their engagement her blessing, and generally kept pushing Regina's live in the direction Cora wanted without considering Regina's own desires or ambitions.