Honestly, how can you ask such a question with such an obvious injury in a tank with so many bigger aggressive fish? If you find him tomorrow with his eyes and guts chewed off, you can safely rule out flesh eating bacteria...
A hospital tank would be ideal. If not available, keep your water extra clean. When my female Festae was wounded, I also raised my water temp and added salt plus extra aeration. You might want to take out the sharp decor from your tank.
Looks like that terror has been fighting, and lost. Keep an eye on the devil. If the terror is smaller then he is a target. Quarantine him if you can and treat with melafix or similar meds. If at all possible, try putting some size on him before returning it to you main display. The wound looks pretty severe from the pics but terrors are tough so a good long stint in isolation should see him through. Good luck.