Mark Hamill proved his alliance to the Light Side when he visited a dying child whose only wish was to meet Luke Skywalker.
He took a shot in the dark and made the attempt to contact Mark Hamill himself (a.k.a.
Hamill will return as Luke Skywalker in Star Wars: The Last Jedi, where it remains unclear whether or not he will remain in the Light or succumb to the Dark Side.
He not only met with the boy, but spent hours answering question after question (sometimes the same ones repeatedly), AS “Luke.”