In season 3 episode 12 of Breaking Bad Mike sits the main character, Walter, down and recounts a story from his days as a beat cop.
He tells the a story of a repeat domestic abuser. Of the multiple nights he and his partner were called out to the home of a large husband who’d beaten his tiny wife. Each night the abuser spent a night in jail, and upon apologetically sobering up, returned home only to repeat the abuse several days later.
Then one night Mike decided that, rather than take him in for the nightly lock up, he was going to teach him a lesson. So instead of the precinct, he drives him into the middle of nowhere, sticks a gun in his mouth and threatens to kill him to put an end the abuse. After hearing the abusers pleas for mercy, Mike concedes and makes him promise to never abuse his wife again.
Two weeks later, the abuser kills his wife.
As he agonizes over his decision to apply mercy to the abuser, Mike concedes he should have gone all the way in putting an end to him and the abusive situation.
He ends his story with this warning- No More Half Measures, Walter.