I believe that’s a huge part of why Thor tries so hard to bring Loki back. He should be furious at Loki. Loki did all sorts of ridiculous horrible things to him and Thor isn’t one to let a grudge go. But he tries to talk Loki out of everything initially, he can’t even stand when Loki is put in the cage, he defends him to the other Avengers in spite of everything, he cries when he realizes Loki is going to kill him, and he still tries to talk Loki out of his plan even after all of that. Yes, there’s a lot of brotherly love still there, but I think a greater part of it is GUILT. He realizes too late that he was part of the problem and he’s a good enough person to want to fix it.
“For whatever I have done to wrong you, brother…I’m truly sorry”
I think he is, but it’s too late. He didn’t properly value Loki when he had him and now he can’t get him back.
It’s too late for that broken bond to be repaired. so much has happened and so many mistakes made by both of them. Sadly this is a relationship that will only be repaired at each other’s deathbed, when all mistakes are recognized and you feel that deep need to make amends.