He couldn't care less what happens to Loki. In Clint's opinion, the worse his punishment is, the better. It couldn't be worse than what he suffered, being forced to kill many of the only people who had ever meant something to him.
But at the same time, he finds himself hoping that it isn't too bad, for Thor's sake. The archer considers the kind, strong, loyal thunderer a friend. And the most important person in Thor's world is about to stand trial.
So when the thunder crashes like a dropped snare drum, Clint can't ignore the sadness in his heart.