You use benign to describe someone who is kind, gentle, and harmless.

A benign substance or process does not have any harmful effects.

A benign tumour will not cause death or serious harm.

Benign conditions are pleasant or make it easy for something to happen.

If you describe someone's approach to a problem as one of benign neglect, you disapprove of the fact that they are doing nothing and hoping that the problem will solve itself.