He lost all of that not by any fault of his own, but because he wanted to save the woman he loved and her sisters, who were being targeted by the Source. He’s manipulated into ‘defeating’ the Source, when really he’s destroyed the previous host of the Source, and now he’s possessed. He’s still himself at first, and he’s desperately trying to tell the sisters that the danger isn’t gone, but the Source is too strong and straight up forces him to stay quiet and eventually takes control. The Source even states at one point that Cole is buried in the back of his head. I remember the Source noting that Cole has become quiet in their head, or something along those lines. It’s very obvious that Cole isn’t in control at this moment.

When Cole does have a moment of clarity, he tries to give the Source to someone who WANTS it, and is stopped by… Phoebe. Also manipulated by evil, but not possessed. She damns him when she stops him from freeing himself. She’s eventually forced to vanquish him, since at that point the Source has a pretty firm hold on Cole. Sure, he’s influenced by what Cole would’ve felt and his own emotions, but it still isn’t Cole. He’s in there, he may react, but it’s the Source just feeling his emotions.

Then he’s vanquished, and he fights tooth and nail to get back home. He wants to return to Phoebe and the family he’s found. There isn’t even a way for him to know that they lost their baby, since that happened after his vanquish. Which means he has to put it together himself. He doesn’t see why they wouldn’t welcome him back, he doesn’t see why Phoebe wouldn’t want to try again. After all, he was possessed. It wasn’t him. They’ll understand that, right??? Nope.

Phoebe’s trauma makes sense, and so does her aversion to Cole. Regardless of how it happened, she still had to kill her husband for the greater good. Then she loses their baby, and to cope she just says ‘well, the baby was never mine’ but it was. It was theirs, and seeing Cole after she’s trying to heal and get some closure hurts. She pushes him away, she calls him the monster, and her sisters support her 100%. Which is fine, she has every right to distance herself from Cole after what they both went through!!!

That being said, the sisters seem to forget that they’d be dead without Cole’s sacrifice. He unknowingly damned himself for them. He suffered and lost just as much as Phoebe, with the major difference being that he was entirely alone. Then he takes on all these powers that he was never meant to have, which is always a recipe for disaster. The power is what makes him absolutely lose it in the end, kinda like Prue with her empathy (which is kinda great considering he did that to her while he was still evil ngl).

Then before he lost it because of all the power, he was ready to leave and move on. He was going to leave San Francisco because he loves Phoebe and that’s what she wants him to do. He only stuck around because her sisters were like ‘actually no, phoebe needs you :)’ and it’s so unfair to him. They have no choice, but every time he finally gets the courage to leave and move on, they pull him back. His descent into madness probably happens so much faster than it would’ve under normal circumstances; unlike Phoebe, he has zero support. It’s why he’s spending half a season trying to unalive himself when he’s immortal.

I firmly believe the sisters could’ve helped Cole, if they wanted to. Their crime wasn’t wanting him out of their lives. It was treating him like he was to blame when it was the only way to save them and he didn’t know what would happen. It was thinking the only option to take care of the Cole Problem was to vanquish him. I don’t remember if they even tried stripping his powers, but if they did they didn’t try very hard. If anything can do that, it’s gonna be the Power of Three.