Hattori Zenzō (Gintama) single-handedly taking down the entire Kiheitai fleet with his immense ninja techniques alone.
River Tam (Firefly/Serenity) after single-handedly butchering an entire army of Reavers.
Sora (Kingdom Hearts) can handle an entire army of 1000 Heartless with little effort.
Goku (Dragon Ball) single-handedly defeated the Red Ribbon Army as a child. Ever since then, he has increased in both strength and power. His skills, Ki-based abilities, and Super Saiyans transformation allowed him to overcome the strongest of opponents throughout his life.
Much like his rival,Goku, Vegeta (Dragon Ball series) is a very powerful Saiyan warrior. His energy based attacks, physical techniques, and Super Saiyans transformations have allowed to defeated countless enemies.
Monkey D. Luffy, Roronoa Zoro, and Vinsmoke Sanji (One Piece) are the three strongest members of the Straw Hat Pirates. They are capable of defeating an army of pirates, marine soldiers, giant monsters, and are able to destroy three Pacifistas when it took the entire crew at their best to only defeat one two years ago.
Rob Lucci (One Piece) is physically one of the strongest characters of the series. At the age of thirteen, he killed over 500 soldiers and a crew of pirates single-handedly. And thanks to his training in the Rokushiki and Devil's fruit ability of Neko Neko no Mi: Model Leopard, his great speed, strength, reflexes, and durability were even enough to bring Monkey D. Luffy to his knees.
Kizaru (One Piece) single-handedly captured 500 pirates during his attack on Sabaody Archipelago.
Multiple Man (Marvel) is literally a one-man army.
With his expertise in weaponry, combat skills, and armed with his magic sword, Jack (Samurai Jack) is able to take on giant monsters, hundreds of robot destroyer drones, supernatural creatures, and even face off against Aku himself.
As The Fastest Thing Alive, Sonic (Sonic The Hedgehog) is well known for using his speed while in ball form to combat hundreds of Dr. Eggman's robots as his speed in his ball form is strong enough to break or cut through their metallic armor. Outside of his speed, he possesses great physical combat skills despite having little to no training in martial arts as seen when he faced off against the Gizoid, Emerl, who possessed all of the abilties of him and his allies.
As shown multiple times in his life, Jak (Jak and Daxter series) has proven to be a vary capable fighter. Thanks to his ability to channel various forms of Eco, melee skills, and acrobatics, he has defeated ambushes of Lurkers, Crimson Guards, Metal Heads, and Dark Makers.
By carrying the Spirit of the Hero, armed with his Master Sword, bearing the Triforce of Courage and mastery and possession of multiple weapons, gadgets, and magical items, Link (Legend of Zelda) is able to overcome countless forces of evil such as monsters, demons, and the undead.
Possessing speed, strength, endurance,his traditional X-buster, and his limitless potential, X (Mega Man X series) is capable of taking on numerous Mavericks, Mechaniloids, and even Sigma however strong they may be.
As shown in the past, present and future, Zero (Mega Man X, Zero, and ZX series) has shown to be strong enough to take on an army of Mavericks single-handedly.
Asura (Asura's Wrath) possesses speed, strength, durability, and stamina far beyond anything one could call human. The greatest assets to his abilities: his Mantra affinity, Wrath, allows him to increase his power to the point where he able to destroy entire fleets, The Gohma: Vlitra, and even Chakravartin The Creator himself.
Ryu Hayabusa (Ninja Gaiden series) is "the Singular Super Ninja" of the world. As such, his skills in martial arts, Ninpo, and weaponry have allowed to defeat human soldiers, cyborgs, demons, and fiends.
Strider Hiryu (Strider series) is a high-tech mercenary of the highest caliber. His skills in martial arts, agility, speed, trick tools, and his Falchion have allowed him to defeat robots, dinosaurs, warships, and even Grandmaster Meio.
Afro (Afro Samurai) is an incredibly talented swordsman. He is strong enough to cut through multiple thugs and warriors quickly and effortlessly.
Kenshin (Rurouni Kenshin) the battosai can dispatch several opponents with little effort only with his sheath.
Kratos (God of War series) is one of the best examples of this ability. He has shown impressive feats of strength and magic in order to defeat hundreds of foes, deities, and even the mighty Zeus.
While Superman (DC) has been described as 'faster than a speeding bullet', 'more powerful than a locomotive' and being 'able to leap tall buildings in a single bound', these are not his greatest feats. When he is under the sun, his power increases exponentially, allowing him to defeat incredibly powerful opponents.
Due to his proficiency with ATs, Agito (Air Gear) can single handedly defeat and kill many adversaries.
The yellow flash Yondaime Hokage, Minato Namikaze (Naruto). If he's so much as spotted anywhere near the battlefields, the enemy will sound the retreat.
Sasori (Naruto) is a powerful ninja and a cunning one at that. The use of his puppets have allowed him killthe Third Kazekage and destroy an entire nation.
The Six Paths of Pain (Naruto) were known for the destruction of the Hidden Leaf Village.
Sasuke (Naruto) is dispatching an army of Samurai with his Sword of Kusanagi: Chidori Katana.
Erza Scarlet (Fairy Tail), alias Titania. She defeated 100 high-level monsters in a row, which was considered impossible, even for the best.
The Jedi (Star Wars) are capable of handling a large army of invading droids.
King Bradley (Fullmetal Alchemist series) is a very powerful Homunculi. He possesses inhuman skills in swordsmanship that allow him dispatch countless soldiers as if it were a mere sport.
Batman (DC Comics) is well know for using his intelligence, gadget expertise, detective skills, athletic prowess, and strong force of will take over come and army of foes and even super-powered beings.
The Incredible Hulk (Marvel) is one of the most powerful beings in his respective universe. His ever-growing rage is able to increase his power to the point where he is strong enough match the strength of beings such as Thor, Silver Surfer, and the Sentry.
Klaus (The Originals/Vampire Diaries) can take on an army of vampires single handedly. (Click to animate)
Buddy Blank (DC) truly lives up to his codename of OMAC (One Man Army Corps).
Captain America (Marvel) easily holds his own against a legion of Hydra operatives.
Big Boss (Metal Gear) is renowned as the greatest soldier of the 20th century.
Guts (Berserk), the "Hundred Man Slayer."
The Bride (Kill Bill) battles the Crazy 88.
Angel (Buffy the Vampire Slayer) was able to single-handedly defeat around twenty vampires and demons while undergoing a period of ruthlessness.
Samus Aran (Metroid) has fought the massive legions of the Space Pirates for years.
Sun Seto (My Bride is a Mermaid) is skilled in swordplay to the extent that she was able to take on and defeat a rival yakuza gang by herself.
Asterix and Obelix (The Adventures of Asterix) are capable of beating entire armies
Madara Uchiha (Naruto) is a very powerful shinobi who uses his ninjutsu to annihilate most of the relatively undamaged Fourth Division. It was strong enough to bring 5 powerful Kage to their knees.
Some SOLDIERs (Final Fantasy 7) are capable of taking on the battlefield alone.
Hayato Furinji (Mighiest Disciple Kenichi) is the ultimate one-man army, able to take on an entire miltary base all by himself and win, as well as use humans like shurikens and strong enough to defeat tanks by himself, all while fighting with his eyes closed and only using 0.0002% of his full power
Honoka (The Third) once destroyed an entire army all by herself with just a single swing of her sword
After years of training, Kenshiro (Fist of the North Star) can easily kill several humans without taking a single hit.
King Bumi (Avatar: The Last Airbender) took back Omashu and kicked out the Fire Nation (for good) by himself in a mere eight minutes, during the eclipse
Snow Demon (Valkyrie Crusade) is know as the One-Demon Army.
Agent 3 (Splatoon) can singlehandedly defeat entire armies of Octarians and the five Great Octoweapons.
Acnologia (Fairy Tail) who is considered the King of Dragons possess ludicrous power that he is greater than the entire formidable armies of Alvarez and Ishgar and the mighty Wizard Saints and the dreaded Spriggan 12
Natsu Dragneel (Fairy Tail) is a top class Fairy Tail member and the strongest demon from the Book of Zeref, his strength is so insane he can take down over 900 highly trained soldiers with just one breath attack.
Saito Hiraga (Zero no Tsukaima) is the current incarnation of Gandalfr: The Left Hand of God. Being Gandalfr grants him incredible physical capabilities and innate mastery of all weapons, allowing him to single-handed fight an army of 70000.