a teacher who is lenient with students who have misbehaved
Many people felt that the punishment was too lenient.
By giving one more person—the executive—the power to reduce (but not to increase) punishments, our constitutions (both Federal and state) seem to be sending an important message: that in a world in which errors are inevitable, it is better to err on the side of overly lenient, rather than overly harsh, punishment. —Alan M. Dershowitz, New York Times Book Review, 16 July 1989
He could trust himself, he said … to be more lenient than perhaps his father had been to himself; his danger, he said … would be rather in the direction of being too indulgent … —Samuel Butler, The Way of All Flesh, 1903
But in other points, as well as this, I was growing very lenient to my master: I was forgetting all his faults, for which I had once kept a sharp look-out. —Charlotte Brontë, Jane Eyre, 1847