Was. Past tense. We all have things in our past, Thor. We all have made mistakes. You learned from them.
You destroyed Asgard so that the destruction already happening would not spread to other worlds. That's a sacrifice. You didn't exactly walk up to Thanos and give him your people and brother with a big bow wrapped around them.
No one blames you, Thor. We all had a chance to kill him. None of us are cold blooded killers. You need to learn how to forgive yourself. Like I did about Bucky.
I don't think you really believe that. If it were true you wouldn't care.