"To take a town, send a legionary. To take a city, send a squad. To take a world, send a company. To take a culture, send a Chapter."The protagonist does far more than pull his own weight. In fiction, it is not only possible but routine for one man to go around and kill literally thousands of people. No one ever finds this particularly unusual, nor does anyone ever wonder about their psychological state, which would certainly be affected by taking so many lives away. The impact of this is lessened if the enemies are Faceless Goons or don't register as human beings who exist solely to provide a Mook Horror Show, but the unlikelihood of one person wiping out entire armies of epic proportions isn't. Often Handwaved or justified by making the character a Super Soldier against mundanes, but this falls apart when Elite Mooks or Superpowered Mooks of equal calibre show up and still get dismantled with ease. In a series aimed at younger audiences, they may simply defeat large masses of people rather than outright kill them. In playing this trope, it is useful to have The Evil Army try to Zerg Rush said character in The War Sequence. This trope caters to everyone's inner Munchkin; 99% of First Person Shooters ever made fall under this. Often goes hand-in-hand with It's Up to You. When the One-Man Army is intentionally sent out to take care of the problem by himself, its a case of One Riot, One Ranger. Villains tend to underestimate this person at first, considering him Just One Man. Compare and contrast Person of Mass Destruction, who's symbolically treated like a weapon by the setting, and Omnicidal Maniac, who is all too willing to push him- or herself into this territory. In the latter case, the Omnicidal Maniac often gains his/her/its kill-count through using WMDs on hapless civilians rather than personally fighting enemy combatants. Of course, being a One-Man Army usually qualifies you as a Badass and Crew of One. However, very few people will respect your ability. Or worse, seek to abuse it because "We Do the Impossible" is in effect. Contrast with the Badass Army where each individual could be considered this but are part of said army, as well as the Easily Conquered World where it's the severely, severely outnumbered enemies who are kicking ass and taking names. If one man makes the army, then you have The Minion Master. Likewise, if one man becomes the army, it's Me's a Crowd. Compare Showy Invincible Hero. See also Conservation of Ninjutsu, which postulates that being outnumbered is what gives the character the advantage. While Real Life examples do exist, this is generally not a good idea in Real Life: the reason military forces tend to work in groups or teams at the very smallest and why police officers tend to call for backup before approaching a dangerous situation is simply that one person is only capable of so much, and may be so focused on one part of what is happening that he or she will have Failed a Spot Check on another, possibly far more dangerous one. As many combat veterans had pointed out, even the greatest battlefield champion can meet an utterly stupid death from a stray bullet, a booby trap, or even good old fashioned disease and blood poisoning from a small wound. For this reason, most of the warfare stunts to put James Bond to shame had been pulled by men who were convinced they were not going to survive. Also, in the case of modern combat theaters, it's more difficult to pull off if any army in the theater has airstrike capabilities, because no real-life One-Man Army can stand up to a bunker-buster bomb. Or, if any force in the theater has nuclear capabilities and delivery capabilities.
— Ultramarines proverb, Warhammer 40,000