adjective
fierce
FEERS/fɪrs/
Displaying aggressive power that is difficult to withstand.
The fierce tiger lunges forward with bared teeth and extended claws.

Etymology
Ferus described what was wild or untamed, including savage or cruel behavior. That idea of wild force connects fierce aggression with the broader use for overwhelming strength or intensity.
In context
them like flames of fire from every quarter. As when a wave, raised mountain high by wind and storm, breaks over a ship and covers it deep in foam, the fierce winds roar against the mast
More examples
- The fierce winds tear branches from the trees.
- The proposal faces fierce opposition from local residents.
- Competition for the final spot grows fiercer each day.
Forms
fierce · fiercer · fiercest
fiercely adverb — With great aggression, force, or intensity.
fierceness noun — The quality of being aggressive or intense.