Green Terror.
I currently have a Midavil (she is a doll so far, a fat doll, but a doll nevertheless), a Jack Dempsey and a Green Terror.
She has the convict and the jack dempsey constantly on the ropes. And I mean seriously she is a furious fish, of course carefully respecting Big Bertha the Midavil. No one messes with her. But she doesn't mess with any of them.
She actually lets them hide from the GT behind her and will often times glide in between and chase the GT off.