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Star Wars: Clone Wars has varying degrees of this trope. Durge is shown (and explicitly stated in other EU material) to be a one-man arsenal, but "only" kills a few dozen soldiers. General Grievous is similarly able to cut through clones and Jedi with his usual psychopathic zeal, but his body count is relatively low. Anakin and Obi-Wan are better examples, a "body count" of droids well in the thousands, but they have their limits and still rely heavily on the armies they command. Mace and Yoda, however, wipe out hundreds of droids without their lightsabers and tear apart entire legions with little help from their soldiers.
Another special mention goes to Yoda. In Star Wars: The Clone Wars, he gets into a bet with Asajj Ventress over whether a certain planet will join the Republic or the Separatists. If he can escape Asajj's best troops, the plane will go with the Republic. Yoda barely breaks a sweat.
King Katuunko: You were right, Count Dooku. One Jedi is not worth a hundred battle droids... more like a thousand.
Can't forget Bumi either, who liberated the city of Omashu by himself. He didn't run from the army. The army ran from him.
While he was locked inside of what was essentially a metal coffin. What did he use to escape, you ask? His face. Really.
According to the Word of God, the reason Piandao is so revered as a sword master is because of what happened when he decided he was tired of the military and became a recluse. The military sent a hundred soldiers. Piandao sent them all back.
Then we've got Ty Lee, the butt-kicking, GenkiDark Action Girl, who takes out an entire group of elite earthbenders by herself in "The Drill".
The whole Team Avatar is this to some degree. In the episode "Earth King" group of kids in age from 12 to 15 year old, just blasted to the Earth King's Palace through a legion of elite earthbenders.
The Order Of The White Lotus is basically composed of these. The previously mentioned Iroh, Bumi, and Piandao are all members. There's a reason their battle with a Fire Nation army that was super charged by Sozin's Comet was a Curbstomp Battle.
The fact that at least two of their own were supercharged as well doesn't hurt.
In the sequel series, The Legend of Korra, there is Lin Beifong. Chief of police, with the ability to Metalbend and Earthbend, her skills become increasingly impressive just by a few episodes. In Episode 7 she's seen taking out a Mini-Mecha all on her own (while everyone else with her held their own but never really took down any of the Mecha), and in Episode 9 she frees her officers from an Equalist base, doing practically all of the work.
Any member of the Red Lotus, and all 4 combined are basically unstoppable.
Tenzin is shown to be such, especially in Season 3 when he easily fends off Zaheer, and it takes the combined effort of all 4 members of the Red Lotus to take him down.
In season 4, Kuvira is shown to be one.
In GIJoe, Sergeant Slaughter was known to defeat whole squads of Mooks by himself. But that's not all. When he was put in charge of training the other Joes, he challenged them to attack him all at once. They took him up on it, and he won without breaking a sweat. (Of course, his Real Life counterpart likely isn't this tough, but still...)
Megas XLR. First episode: On one side, Coop and a nameless sidekick mecha. On the other, a large army of alien mooks and their commander.
Kiva: Look at them all. These odds are awful. Coop: You're right, it is kind of unfair. * knocks sidekick out* Now it's fair.
In Invader Zim, it's shown that apparently a single competent Irken Invader is capable of conquering a planet by themselves. Helps that they do have some impressive technology at their disposal. The main character has even better technology that he's engineered himself, but being a Chaotic StupidGenius Ditz has no way to use them effectively (though he's still pretty dangerous at times).
The title character of Samurai Jack, with only a couple prepared traps, single-handedly destroyed hundreds (if not thousands) of Kill Bots in the third episode.
Not only that, but the last few Kill Bots actually took a step backwards trying to running away. Jack said "No, there is no escape." and ruined them.
Once, he managed to beat a moderately large army of robots with literally no effort at all.
In "Birth of Evil", Aku becomes a literal example, splitting himself into an army of man-sized duplicates of himself in armor. (However, seeing as Jack's father still defeated them all, he qualifies for the Trope here as well.)
Maggie Simpson, despite being a baby, can take out a group of mobsters with a rifle.
Brock Samson, or as he's been referred to by The Monarch, the Swedish Murder Machine.
In Teen Titans, Robin, definitely. In Apprentice, he takes down a whole army of Sladebots by himself, brutally, and in the second part of the season finale, he takes down his entire team. By himself again. When they were all attacking at once. And it's a Curb-Stomp Battle.
Alice of Superjail is the only guard in a demented facility full of the very worst psychopaths not fit for regular prison. And she has no trouble kicking all their asses, and keeping the prison in relatively normal condition.
Tai Lung in Kung Fu Panda has his own prison and is guarded by one thousand guards as well as being held completely immobilised. When he gets free of his shackles, he beats up all the guards in a matter of minutes. Granted, he finishes the job with some dynamite that sends a large number of them flying at once; it might have taken up to another minute or so otherwise.