What is a noun for "nice revenge"?
Solution 1:
Reciprocation is the word you're looking for. In simple words, reciprocation is the act of reciprocating.
Reciprocation: the fact of feeling or behaving towards someone else in the same way as they feel or behave towards you. [CED]
Reciprocation often has positive connotations. Retaliation is often used in the same contexts with negative connotations.
You could also say return the favour.
For example, if someone does you a favour, you can reciprocate by doing the same thing (good for good) or you return the favour.