Fierce (adjective)

1. Having or displaying an intense or ferocious aggressiveness.
2. Intensely or extremely eager, passionate, or determined.

Origin:

Middle english fers, from old french fers, from latin ferus "wild".

Examples:

1. The competition was fierce.
2. The animal had a fierce look in its eyes.
3. The storm was fierce and dangerous.
4. He had a fierce determination to succeed.
5. She had a fierce loyalty to her friends.