Is the character a fully actualized person? Or just a mess of stereotypes thrown together?
Is the character defined solely by one aspect of their identity (i.e. are they the gay one? the Black one? the girl?)
Is the character played by an appropriate actor? (See: Rebecca Romijn playing Alexis Meade, a trans woman on Ugly Betty when there are trans women who could have filled that part)
There’s probably a better checklist somewhere but please don’t just think media representation is about a character BEING there.