"You are a gigantic infant, brother." Frustration wasn't helping. It never helped. Magic required focus and precision, and frustration sabotaged both.

Loki took a breath and closed his eyes, both to rely on other senses and to ignore Thor's ridiculousness more easily, then tried again. One more try. This spell was less physical, in a way, more trying to convince the cells to knit back together. Persuasion rather than force, which at least had the benefit of being closer to his actual skill set. Stop being assholes, cells.