I think everybody is guilty in his own why.

A mixture between Odin, Thor, The Warriors Three And Lady Sif.

Not so much Frigga, mostly because we don't know much about their relationship.

Definitely put a lot of blame on Odin.

Mainly Odin, The Warriors Three and Lady Sif, Thor, and The People of Asgard.

Okay it's definitely his not father fricken bit his head off at that one part right before Thor gets banished he says quietly"father." Then odin snaps back HEEEEEEEEYEEYARGHHHHHH! What an asshole, pardon my french.

lol ur right!

mainly his dad

personally i'd have to say odin, because his parenting skills really suck. I can't put any of the blame on thor or frigga. they were the only two who ever tried to reach out to him.

I heavily blame Odin. I'm sure some of you fans can agree with me?

Odin and basically all of Asgard excepting Thor favored Thor --> Loki blamed all of Asgard including Thor --> Thor is an oblivious angel --> Loki grows exceptionally bitter and hates pretty much everyone except Thor and his mother.
So I don't blame anyone but Odin. But everyone except Thor is at fault. If that makes any sense ugh whatever it's late