Yes, RETRIBUTION is a Scrabble word!

Letter values in Scrabble US: R 1, E 1, T 1, R 1, I 1, B 3, U 1, T 1, I 1, O 1, N 1.

Is it a valid word?

RETRIBUTION is a valid word in the official Scrabble dictionary (US), the UK Scrabble Dictionary and Words with Friends (ENABLE).

a justly deserved penalty
the act of correcting for your wrongdoing
the act of taking revenge (harming someone in retaliation for something harmful that they have done) especially in the next life; I will repay, saith the Lord"--Romans 12:19