Is the Night King truly evil?
When Mance rose to become King above the wall the wildlings were facing a Winter they weren't likely to survive as separate clans North of the Wall and Robert's rule had become a joke and his heir was a sociopath South of it.
As time has went on the Night's King has grown stronger and stronger as the houses of Westeros rip each other apart. And we know that the only way to stop the army of the dead is for the continent to stop its bickering and unite. Just like in the end the only way for the Children of the Forest and the first men did when they put aside their war to fight which in turn lead to peace between them.
So in the end is the Night's King really the bad guy or did the old gods just allow the ultimate weapon of the Children to rise because the people were at a crossroads and basically needed a crisis to make then sort their shit out?