One must make the difference between "warrior" (one who enjoys fighting, indeed is only really living when his system is saturated with adrenalin, ie. he's fighting or fornicating. Note that the "he" is the generalised form, not a statement that women can't be warriors) and "soldier", one who fights for his living. Hollywood prefers the former, as they make better action heroes, but civilised armies show a marked preference for the more disciplined, less flamboyant killer.
Since I tend to use the universe, and human stupidity (well, actually, sentient stupidity; no race could rise to sapience without direct divine intervention or stupidity as part of the education process. Chrispy's second law.), greed and egocentricity. So there's little need for a separate military subspecies; you select among generalists for the most suitable. Fast reaction time, evidently, but more than that the ability to integrate information and make rapid, generally correct decisions. Which ability is cogent for all unpredicted emergencies, so you're only choosing for destructive activity to be a high priority.
Physical strength and size are less important; there will always be someone stronger. If the protagonist is faster, more determined, more vicious and has the common sense to fight when victory is assured he'll win over the giant monster, however well armoured; the extra size makes a bigger target. Training and tradition make up the rest; and there the male of the species has a notable advantage, at least over fertile females; there isn't the lost time in pregnancies.
But the most important is the ability to make instant decisions, as to actions or whether something is friend or foe; considered choices in a minimum of time. Just destroying everything is a waste of energy, and ultimately self defeating, but trusting the wrong person is a recipe for a short existence. There again, that talent , the 'anti-dither', is useful in a wide selection of situations.