Perhaps my favored characteristic of the Alpha hero is his possessiveness. I'm not even going to think about what that says for my psyche. All I know is that I love the moment when the hero growls, "You're mine!"
Even before he's allowed himself to admit he loves the heroine, he just can't take the thought that any other man will be spending time with her. From Nora Roberts' historical Lawless:
She stepped closer to stab a finger at his chest. "If I allow Samuel to kiss my hand, that's my affair. He's asked me to marry him."
The last thing she expected was to be hauled off her feet so that her slippers dangled several inches from the ground. "What did you say?"
"I said he asked me to marry him. Put me down."
He gave her a shake that sent hairpins flying. "I warn you, Duchess, you think long and hard about marrying him, because the same day you're his wife, you're his widow. That's a promise."
I know, I know. In real life, I'd be calling the police and asking for restraining orders just like you. But in fiction, those scenes just sing through me.
Maybe it's the combined force of all those dates and boyfriends who made it known that I was their girlfriend, but if I wanted to go further than that? "I need space, man." And then they'd look at me as if I was a new and not very attractive form of fauna. "What the hell's wrong with you, anyway? Why do you women always have to get all weird?" Grrrr.
The Alpha may have issues with commitment at first, but once it's made he'll keep it to his pain. And do anything he can to make things right. Yes, I like possessive heroes. Sue me.