let someone off
Definition: to give someone a lighter punishment than expected or no punishment at all.
(This phrasal verb has more than one meaning)
E.g.1: It’s not fair! You always punish me and you always let him off. He broke the computer, not me.
E.g.2: The thief only got 3 months for attacking the old lady. The public were angry because they felt that the justice system had let off a man who would commit the same crime again and again.
This phrasal verb can be separated. (E.g. 1)