Pugnacity (noun)

1. A disposition or tendency to fight; aggressiveness; combative readiness.
2. A natural inclination towards aggression or combat.

Origin:

From latin pugnacitas, from pugnax ("fond of fighting"), from pugnus ("fist").

Examples:

1. The pugnacity of the boxer was evident in the ring.
2. He had a pugnacity that made him a formidable opponent.
3. The pugnacity of the animal made it difficult to handle.
4. His pugnacity was both a strength and a weakness.
5. The pugnacity of the opposing team was intimidating.