Term to describe “revenge through sexual intercourse”?

What term can be used to describe someone who, to take revenge on or extract payback for (perceived) past wrongs done them by their (unfaithful) romantic partner, goes off and has casual sex with someone other than their customary partner?

Solution 1:

First, I would say that this person has his/her priorities mixed up. Then I would say that person is vengeful:

Desiring vengeance; indicating or proceeding from a desire for revenge.

vindictive and spiteful work as well:

Disposed to seek revenge; revengeful; marked by or resulting from a desire to hurt; spiteful.

Other similar words are resentful: full of or marked by resentment or indignant ill will; "resentful at the way he was treated".

Or, they might not be angry at all, but maliciously calculating.

There are also bitter, hurt, wounded, angry, offended, put out, jealous, pissed, incensed, grudging, aggrieved, indignant, pissed off, irate, miffed, embittered, unforgiving, and peeved, but not all of them apply equally.

I would not differentiate on th basis of gender. What's good for the goose is good for the gander.

Solution 2:

Talionic: adj. -pertaining to revenge in kind; retributive; like for like; pertaining to revenge in kind

&

Talionic: Of or pertaining to the law of talion, or to the rendering of like for like.