Blackbelt IMO , i got one aswel as a Oscar and they get on very well .
Only time there is trouble is when it feed time and they push each other about fighting for food but other than that they get along well .
I also have 1Jag' , 1 JD' , 1 Port Acara , 2 Common Pleco , 1 Four Line Pims , 1 Chocolate Cichlid , 1 Firemouth Cichlid , 6 Silver Dollars , + others , in with my Blackbelt Cichlid and hey all get along very well .
No really fighting between them , just a little chasing a pushing about but NO jaw locking or biting .
So getting a Blackbelt Cichlid ~ aslong as its a very placid one it should be fine with your Oscar .