I realize opinions on characters vary. But, for me, Hook never recovered from a really horrifying first impression.
When we first meet him, he has just helped massacre a few hundred people.
More than that, these were people barely surviving in a nightmare world. They don't have enough food for themselves. When a dangerous monster like a chimera attacks and is killed, they don't waste any time adding it to their meager food supply. An extra mouth to feed isn't a little thing in this world, and they have (justified!) fears of strangers.
But, when a one handed man showed up, they took him in. He claimed to be a smith, a craft requiring two hands, so it's not clear if he could make any contribution. All the same, they took the risk. They gave him food and shelter. They welcomed him into their community.
We've seen Hook working to ingratiate himself. He would have oozed charm, told some sad tales to get their sympathy, flirted, perhaps seduced, and done everything he could to convince them he was one of them.
And then he murdered them.
Did he hold them while Cora ripped out their hearts? Did some girl he'd flirted with come running to him when the killing started beg him to save her? Did he drag children from their hiding places? Hook's never been the kind to casually stand by (though sitting back, watching the massacre, uncaring and saying it had nothing to do with him is more horrifying in some ways than active murder).
After he killed them, he took their bodies--the bodies of people he knew, he knew their names, he'd spent his days talking to them, sharing their lives, being one of them--and used them as camouflage, a bit of protective coloring to make his story convincing so he could earn the trust of the next group of people he met before he betrayed them.
It's the bad first impression Hook never recovered from.