Like I said before you can follow the path of light and still use dark side powers. The lore split the force into 2 parts Light (healing and telekinetics) and Dark (Damage and other forms of sith alchemy), but luke used a variant of force lightning that was more towards the light side I believe. But any ways you don't have to be evil to use the dark side of the force for example my force alignment is light on my sith inquisitor and yet I still can use force lightning, Revan can use dark side powers and hes good and so can Luke.