I thought I couldn't breathe without you,

But I'm inhaling.

You watch movies and you see this guy leaving this girl citing 'I'm not good for you, if I stay, I'm just going to hurt you more'. Or something similar. And this girl, well, she was stupid enough to fall for this guy. Who hurts her time after time. But she reserved a spot for that wretched guy somewhere in her heart. And she always comes back to him.

Until the guy walks away. Walks away because he thinks that he's just going to 'hurt' this girl if he stays.

You know what I think of this guy?
He's full of himself.

He's painting a picture as if he doesn't have any control in hurting her. So solution? He hurts her more.
He acts like as saviour to her. Trying to be a bigger man by walking away.
Pff.

The fact is, he's a coward. Selfish and cowardly, nowhere near noble.
If he doesn't love the girl, just admit to that fact. And leave. Don't sugarcoat it with the term 'walking away'. It's degrading for the girl. He strung her along, he hurt her countless times, she stayed through it all, and still, he gets to be the noble one. Because he can't stand to hurt her one moment longer, he walked away.

Well, no shit Sherlock. If you don't want to hurt her, don't. It's that simple. The fact is, your own selfishness and ego prevented you from treating her right.
You know that.
You don't get to release your own conscience by telling yourself and telling her, that you're doing this for her benefit. You lost your right to that when you pretended to love her.

Never give person false hope. It hurts.
You're the evil one.
You're the bad guy. You abandoned someone who trusted you.

She may never recover. She's broken because of you.
And you get to walk away unscathed while she struggles to pick up the pieces.

Make no mistake. You can trust no one in this world.