The latter end of 40, unshaven, harder than titanium, operator who will outperform a dozen 20-something experienced soldiers, never had a broken bone or major injury, except for that rare form of horrible trauma that made him even more efficient and capable than ever before and who has the ability to make everybody with an officer badge lose fifty IQ points by simply walking into the room.
Any situation he happens to walk into becomes a task primordial to the survival of the US, Western Civilisation or even the entire world and comes equipped with a handheld radio with unlimited range and battery life that can magically summon anything from an observation drone to the entire US bomber fleet to take out a target. He's the guy with the designer glasses and a Hard-Rock Cafe T-shirt from an exotic location under his body armour in a sea of camo uniforms.
When things go wrong, he automatically assumes command, telling 17-year old baby-faced Captains what to do and earn their undying admiration. And when a four-star General chews him out, he'll grimly remind the general that he single-handedly saved an entire brigade of Marines, while the obviously incompetent general was too busy sucking up to the President which always happens to be the wrong guy from the wrong party ...
No matter where you dump him, he knows the local lingo and customs and can blend in by doing absolutely nothing, except when terrorists are nearby who instantly pick him, and is often the last mistake they make.
Doesn't matter how many people he tortures, stabs or shoots, it's always for the greater good. He as a special ability that allows him to bond with locals in such a way that terrorists, insurgents or government troops will murder them within the week, adding more trauma that raises his skills so much it makes a bloodlusted Super-Sayan look like a Quaker in a deep coma.
He has a patronizing respect for ordinary grunts who admire him, short of pure homoerotic love, which doesn't exist in his universe and officers hate him for being a rugged individual who doesn't answer to nobody but the right thing and is never wrong, never makes mistakes ...