this is the way i would say about the meanest (1 being the meanst)
1.undulated
2.queen
3.clown
4.bursa
5.bluelined
6.Assasi
7. huma huma
8.niger
9.black trigger
10.Rectangular
11.Bluejaw
12. pinktail/whitetail
the Rectangular will stay rather small for a trigger but you must understand that every animal is different, so before you buy it watch the way it acts at your fish store, the one at mine is rather nice and living with a small grouper