Yep definitely a pavona or lepto, though they really are the same thing in more ways than they aren't. Pavona typically have longer tentacles like what you're seeing however that is just a generalization. I could definitely see it taking out sps but it seems doubtful that is caused the death of the frogspawn, however that coral does seem to be going to battle and the physical warfare isn't the only thing going on so who knows.
If you want to remove it I'd consider taking out the rock it is encrusted to. It is a beautiful coral and could be isolated or sold to someone who has the space to keep it isolated. If you want to kill it there are certainly many methods that are easy as pie but I would try to keep it alive myself.