It's a rodent. Calming down isn't something they usually tend to do. But you could try exhausting it. Find a target and have it practice electrical attacks until it just can't anymore and maybe it'll be too tired to do anything else. No Pokemon I've ever met would turn down a suggestion like that anyway.

[She plucks a ball from her belt and holds it up to her eyes while she talks.]

Ah, there you are. Megasoma, get her!

[She hurls the ball and a giant stag beetle pops out. He flexes once, twice, Tower roars at him, and he turns and smirks at her.]

Oh for... Would you stop strutting around and hit her?