Best level 6 unit.

#1(1) Nagas, defeated: (all)
#2(2) Dark Knights, defeated: (3;4;5;6;7;8;9)
#3(3) Champions, defeated: (4;5;6;7;8;9)
#4(4) Ifrits, defeated: (5;6;7;8;9)
#5(5) Psions, defeated: (6;7;8;9)
#6(6) Unicorns, defeated: (7;8;9)
#7(7) Skorpios, defeated: (8;9)
#8(8) Wyverns, defeated: (9)
#9(9) Cyclops, defeated: (no one)

Since Psions attack everyone around them, this check doesn't give a complete assessment, only a partial one. For a complete comparative assessment, you need to assign scores from 1 to 9 for each unit on several points and see who is better. This "mochilovo" (brutal combat) is just one of the points. Another example is the cost of construction, taking into account the cost of all buildings needed for it. (By the way, Dark Knights are undead, which is a minus for Morrol if he adds them to his army).

P.S. But this is, of course, the main point of the rating (My choice is Nagas and Psions).