In all three of these species it’s only the males that have horns, and they’re used against each other for dominance.
Kudus have large wide spiral horns with a ridge along the length. Fights among males involve lunging, horn clashing and wrestling with locked horns. Deaths occur from stab wounds and when horns become inextricably tangled.
Bushbuck have twisted and very shallowly corkscrewed horns. In serious fights they engage horns and try to push and twist each other off balance. At the highest intensity they lunge and stab, and this can be fatal.
Nyalas have shallow corkscrew horns with a ridge up the outside curves, and short yellowish tips. At highest intensity a status display involves two males raising their manes and parading slowly past the other with exaggerated high steps, heads down, horns forward and tails curled back. Sparring involves head pushing and horn clashing. Serious fights are rare but fierce, and can be fatal.