In Greek mythology, the goddess of retribution, who especially punished hubris
Violent acts carried through in defiance of the gods and human custom.
The goddess of divine retribution and vengeance.
Goddess of revenge; retribution; inevitable consequence.

ETYM Latin, from Greek Nemesis, orig., distribution, from nemein to distribute. Related to Nomad.
(Irregular plural: nemeses).
A formidable opponent; an arch-enemy.