>>24962144If Bro doesn't know that Anon is inside the mimic, tell him so. With that, going all out on offense isn't a very good idea since you don't know how bad your attacks may hurt Anon. Also, we know that shooting it until it dies isn't usually a good strategy against bosses.
That said: Bro leashes out a torrent of Muddy Water to reduce the monster's accuracy and sight, while Dede uses Nuzzle to deal some weak damage and paralyze the monster, and get close to the monster... and the zipper.