If I walked away from somebody who made me feel like absolute shit, am I the one to blame?

আপনি should have explained how আপনি felt, to give them some closure.

But other than that, not really

Nothing's your fault; আপনি should always walk away from people who make আপনি feel like shit because they're bad for আপনি and আপনি should surround yourself with positive people. I think আপনি should be straight with them now though and tell them why আপনি stopped hanging out with them, for closure.

আপনি have no obligation to be nice to someone who does nothing but hurt you.
Now, if that person does do nice things for আপনি once in a while, he/she may be trying to be nice but is having a hard time with it. আপনি should do what আপনি think is best, but try to think about it before আপনি do it.

If your relationship with someone is destructive then আপনি have every right to walk away. But I think আপনি do owe them an explanation. Just so that আপনি put it all behind আপনি and সরানো on. Even if they respond badly to what আপনি say, আপনি shouldn't feel bad about it because আপনি have done your best to resolve the situation.

আপনি should tell them the truth.... maybe they feel like its a slap in the face to them. They are wondering. Dont worry আপনি are not the one at fault... it would though be a good idea to tell them why আপনি have changed sides.?? One thing for sure আপনি do not need to feel guilty because that will just eat you. its human nature to change so its fine.

hell to the fucking no

No way! Why should আপনি stay around people who make আপনি feel like shit? That's only a stress booster not to mention it would be super annoying to have to face someone who always shuts আপনি down. But if they ask আপনি that again, explain why. Hopefully, they understand. And they might stop doing whatever it is that's making আপনি feel like shit. Sometimes, আপনি have to point out a flaw.