Defectivehorn Apostle here, I feel I should give you an update about more newer horns that seem to stand out to me among my herd. First of all, @muscle_Horn does have some rivals. One is "Willow" who is a defective musclehorn and an odd one too. 1/?

2/? Willow is built for speed, agility and flexibility. For a musclehorn she is taller, thinner and notably weaker than a normal musclehorn (still stronger than a human however), but she is FAST. There is no other musclehorn faster than her.
3/? Willow wins by staying out of reach and wearing down her opponent with rapid blows. Also I do mean she is flexible! I think she has extra ligaments that allows her to contort in ways I didn't think possible. She rarely takes a hit due to it.
4/? Then there is Luna, Physically, she is not a defective at all. Outward wise she is the prime example of a Musclehorn. Her mind is another matter. Other than takeing care of her basic needs and reacting to threats to her herd, she has no will of her own.
5/? Her lack of drive could classify her as a defective but the other horns don't seem to mind it so much. Luna learns quick and in time rival @muscle_Horn in time. How ever she seems to have no desire to dominate anything. She does what is commanded to you for good or bad.
6/6 Luna is more like a machine than a horn sadly. There is little I can do to improve her will so far. I will inform you of more once I figure out the more interesting horns I have now.
Willlow sounds like a strange horn indeed. I wonder how a herd filled with willows would fair against other, less defective, herds. After all, a musclehorn's muscle is not just for combat against other herds indeed herds rarely actually fight in the wild since they tend to stay far apart and distinguish each others' territory by smell) and that muscle is also put to use to build, tear town, transport, hunt, etc. Perhaps a herd of Willows would have to become more aggressive and steal other herds' food to live well...
As for Luna, I imagine the haremhorns treat her like a very well behaved musclehorn. Musclehorns somehwhat lack a strong sense of will in the first place and are easily lead (and scolded) by the haremhorns. Perhaps Luna's "bullyable" setting just got set too high in the egg. ;ww;