KanjiJLPT N1
Fierce

fierce, rave, rush, become furious, wildness, strength

Mnemonic

A beast spots a child creeping toward its dish of bloody scraps. In an instant it turns fierce beyond reason—fangs bared, hackles raised, a thunderous roar shaking the walls. The child stumbles back, terrified. A beast is never more fierce than when someone touches its dish.
Additional thoughts
Picture a massive wolf-like beast hovering over a food dish, a small child reaching innocently toward it, and the explosive ferocity that erupts. The contrast between the innocent child and the savage beast makes the scene unforgettable.
Quick recall
A beast goes fierce when a child dares touch its dish.

Details

The keyword for 猛 is fierce. This kanji conveys a sense of intense ferocity, violence, or overwhelming force. It describes something that is savage, vehement, or extremely powerful in nature, whether referring to a wild animal's temperament, a raging storm, or a person's aggressive and unyielding spirit. It carries connotations of being bold, daring, and relentlessly forceful.
On'yomi
もう