I've had 2 VERY aggressive fronts over the years. One was a huge burundi male that I got as a little fella and had for years. The other was a large wc mpimbwe male that I got for some females I had. The burundi lived for years with the same tank mates and no problems, then one day he realized he was big stuff and started killing his tank mates one by one. He was 12"-14" at the time and was in a 300 gallon tank with only a few large tank mates.
The mpimbwe male was trouble from day one. He would kill any other frontosa, male or female as soon as they were in the tank. I tried dither fish (silver dollars) at the suggestion of a few experienced hobbyists but he ignored them. I could keep him with anything but another frontosa, even some smaller trash fry I was hoping he'd eat. They were safe as could be with him!
All the other frontosa I've ever had, including the two groups I have now - Moba & Smazi, have been peaceful and no problem. I have bought all those no problem fronts in groups, I don't know if that makes a difference or not. I've been able to keep many different types of fish with these fronts with no problems at all.