For me, Broken Heart confirmed this. This is the problem when you put all your eggs in one basket. Hook was solely good because of his "love" or rather obsession with Emma (and because he'd never truly get his revenge.) Why do I think so?
Nimue has never stayed from her desire for revenge and has contually gone with it. Once she had the power, she did as she said. She destroyed the threat (Vortigan) and would give power and things to those who needed it (which is like Rumple teaching others magic and making deals). Her love for Merlin never swayed.
Rumple gained the power and he was finally able to defend himself and enact his anger towards those who he felt wronged him. He had beacons of love for Bae and Belle.
Emma still loved Henry and Hook and pretty much everyone else to a certian degree. She was simply walling herself up again to try to fix her mistakes.
All these DOs are simply themselves with added liberty and a slight addition to their worse traits.
Hook seems to have no veil of love around him and used Emma and hurted Emma. Even Rumple didn't verbally crush Belle like that. Nor Nimue to Merlin. Or even Emma to Henry and Hook. Does he even truly love Emma? Or is he confusing it with obsession? Why would he say such mean things? And no, he isn't possessed Hook fans, then you'd have to add that to Rumple, Nimue and Emma.
I think that he was sort of redeeming himself in season 4, but he knew he was a villain still. He may have helped Ursula, but he was also quick to point a gun at her head! The woman who he had wronged, he was going to kill or at least threatened. No matter how many times Emma tried to call Hook a hero, he knew it wasn't true. No matter how lovey-dovey they are, that doesn't relate to redemption.
I know there's often a train of thought about Regina's redemption not existing and Rumple's not existing, but then I will say despite shippers and fans alike, that Hook's never existed except in miniscule and this episode proves that. He has as much "tallies in the redemption column" as Regina and possibly Rumple.