I'd have to say the Grammodes is by far the most aggressive cichlid I've ever kept. POUND FOR POUND, they are ferocious!
A breeding pair is a nightmare towards other tankmates, even in a 270 gallon. They grow extremely slow unfortunately, but maybe that's a good thing?
But if we're talking about what fish will get the job done.. I'd give it to the Dovii. While jags, Haitensis, beani, butti, and red devil are right behind it.