Snake doesn't have special powers like the members of the Cobra Unit, or Volgin. But Snake didn't run like a Big Loser coward from physically superior opponents. Snake was man enough to do what needed to be done.
Snake's victories during Operation Snake Eater proved that it's not the size of the dog in the fight, but the size of the fight in the dog. For example, Volgin was bigger and stronger than Snake, but Snake didn't flee for his life like a Big Loser coward. Snake fought like a man. Snake won against the larger opponent during their final confrontations because Snake had more fight in him than Volgin did.
Volgin feared Snake so much that he demanded that Ocelot shoot Snake. When a larger man fears a smaller man, you know the larger man is a Chicken-**** Koward and a Kowardly ****. When a man needs a gun in order to win a fistfight, you know he's some weird Mr. Potato Head coward that fears getting beaten up into a pile of mashed potatoes. What a coward.
As long as you don't behave like a Big Loser coward, as long as you fight with your balls like a man, your opponents will be the true cowards as they fear the size of the fight in you, and you will become legend like Big Boss. Which is superior to being a Big Loser coward, or some Chicken-**** Koward, or some Kowardly ****, or some Mr. Potato Head coward. All of whom will never be legend or find a woman that loves them since no woman wants to be with a coward that fights with his head instead of his balls due to having no balls. EVA admitted that she is in love with Big Boss, but no woman will ever love Volgin, that Big Loser coward, that Chicken-**** Koward, that Kowardly ****, that Mr. Potato Head coward who needs a gun in order to win a fistfight because he fears getting beaten up into a pile of mashed potatoes like a coward.