They were, she realised, her nemeses made flesh: one black, the other white; one male, one female; one the taker of her virginity, the other taker of her love.
Italics in the original. Of course, the italics note a Latin word or phrase (the novel is set in the Roman Empire in the late first century), so strictly speaking, this isn't an English plural at all. Have I wasted enough of your time yet? Okay.
 Unnecessary - there is only one Goddess of Vengeance (capital N) and (one hopes) only one thing fated to destroy you. One day I'll find myself having to describe a group each of which is facing their own, individual nemesis and have to get off the fence, but until then I'm undecided.
 Plural: gladiatrices