He seems to have a propensity to fight.

Propensity : an inclination or natural tendency to behave in a particular way.
Scepticism : a sceptical attitude; doubt as to the truth of something.
Penchant : a strong or habitual liking for something or tendency to do something.
Aversion : someone or something that arouses a strong dislike or disinclination.
Proclivity : a tendency to choose or do something regularly; an inclination or predisposition towards a particular thing.

Antonym of Propensity is Aversion