Jaguar and oscar in 55 gallon tank.?

I have a 12 inch oscar and a 5 inch jaguar in a 55 gallon tank soon getting a 75 gallon, and I do have plenty filteration but my jaguar is beating the crap out of my oscar he is really aggressive I have tried rearranging the decor thinking he was fighting over territory but he just does it for fun. So before he kills my oscar I think I'm gonna get him outta there but I wanna know what the most aggressive fish I could put in there that can hold its own I was thinking of a wolf fish but figure I would do research and ask some people any help would be great.