Zeruiah ... Joab ... Abishai ... Asahel ... Abner

Asahel was swift in his feet like a wild gazelle

Here Asahel is compared to a gazelle, an animal that runs very fast. AT: "Asahel could run very fast" (See: rc://en/ta/man/translate/figs-simile)

This small, four-legged animal, with two long horns on its head, runs very fast.