Yes, SULLIED is a Scrabble word!

Letter values in Scrabble US: S 1, U 1, L 1, L 1, I 1, E 1, D 2.

Is it a valid word?

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

place under suspicion or cast doubt upon
make dirty or spotty, as by exposure to air; also used metaphorically
charge falsely or with malicious intent; attack the good name and reputation of someone