PCS *nḳm ‘to take revenge’ is clearly related to Gez. ḳim ‘revenge,’ taḳayyama ‘to take vengeance’. Probably, n- in the CS forms represents a fossilized reflexive marker (Nöldeke (1910:180)).
Akkadian
naḳāmum - to take revenge
(Durand 2000:234, Streck 2000:108‒109)