“I got mad at Rumple for how he treated Zelena in the flashbacks. I understand she couldn’t cast the curse, but he didn’t have let her get out of control/egg her on. He raised a kid to age 14, she was emotionally 5, he could have helped her mature.”
He’s the Dark One. The way he treated Zelena was wrong, no question. I’m not going to defend it, but can understand his mindset in doing it. Zelena was the type of person that bought into Rumple’s darkness. It seduced her, after Cora that became a turnoff for him. She was also her hellbent on taking down Regina after he told her she wouldn’t be casting the Curse. Keeping her around would have compromised Operation Find Bae.