(Death to the Horse-men! is quite unambiguous, no?
Lol!

Hmmm, but that would make Ugluk's ability non unique, tbh.
Then, after reading your words, I went straight forward to two thoughts, about two towering giants:
Achilles vs Boagrius
https://www.youtube.com/shorts/asKgbIrCoD4And, David vs Goliath

Both representations, use spear and sword and shield, apparently using the spear for the first assault.
What if this brutes can be customized, to take spear or sword and shield, the great shields of the uruks seem rather good for them.
If the player chooses the spear, they could deal more damage to cavalry and make their fellow dunlanders fiercer, as Boagrius does when yelling to its people.
If the player chooses instead sword and shield, they could -and i will quote you, dear Elendil- grant them or surrounding Dunlendings some kind of resistance to trample damage. Both abilities, should be activated, thus letting balance to happen
And the third option, those with the enormous axe!
I think this can make more sense for this unit.