I think the aggressiveness of Queen has been highly exaggerated. It's true that it's one of the most aggressive triggers of all, but that doesn't mean that it is a ruthless non-stop killing machine. I've seen people successfully keeping a juvenile Queen with aggressive/semi-aggressive fishes. However, I wouldn't put anything with an adult Queen. Adults are definitely a lot more aggressive and unpredictable in terms of their behaviors. It's simply too risky. Also, they do get big (20"). If you want to keep a Queen, it has to be either a medium-sized species tank (around 100g) or a very large aggressive community tank (>400g).