informal to criticize someone or something very strongly: Unfortunately, if he doesn't agree with you, he tends to tear into you.

To "tear into" generally refers to attacking, criticizing, or beginning to do something in a very energetic, aggressive, or eager manner. It can be used to describe physical actions, like tearing into a package or a meal, or non-physical actions, such as tearing into a task or tearing into someone during a heated argument.