Which was hilariously spoofed in "The Ember Island Players," with a big muscular guy playing as Toph. While most of the characters overwhelmingly hate their character depictions, Toph, in fact, loves hers.
She's also one of the two most powerful Earthbenders in the world, tied with King Bumi. They once had a fight to determine who was the strongest. They wound up having to stop in the middle because it might have given away their location. But they couldn't hear Sokka telling them to stop, so every other good guy and member of the White Lotus had to stop them. They're later seen planning a rematch.
In Sequel SeriesThe Legend of Korra, Korra displays this trait as well. When the White Lotus Society first meets her, she is already bending three elements with skill...at about age four.
8-year-old Bobby. Neither a little girl nor quite possessing super strength, but giving the squeaky-voiced little brother of the group a magic caveman club that causes earthquakes on impact has much the same "gotcha" effect.
Sandy Cheeks of Spongebob Squarepants is clearly Bikini Bottom's strongest resident, occassionally challenging massive, heavily muscled fish and Larry the Lobster to weightlifting challenges.
Danielle in Danny Phantom. Being a clone of the main hero gives her all the powers she needs to butt kick.
Shayera/Hawkgirl in Justice League. While she is an adult, she is easily the tiniest (and most smash-happy) member of the Original Seven. Justice League Unlimited also throws in examples like Supergirl, Stargirl, and Black Canary.
Lisa Simpson in the Treehouse of Horror episode where she gains superpowers and becomes Clobber Girl.
Panini from Chowder - She gives a beating to Gazpacho and Gorgonzola in "The Bruised Bluenana" and "Hey Hey It's Knishmas" respectively.
In one instance she threatens Chowder into holding her hand while walking home.
In Tom and Jerry cartoons, Jerry the Mouse is usually on the receiving end of pounding and can only get upper hand through cunning and agility. But God help you if you hurt his friend - he will trash you and wipe the floor with your blue furry ass. Moreso with his cousin who doesn't even need the adrenaline surges to pummel cats.
Jungle Boy from Johnny Bravo, although ironically enough Johnny Bravo is able to injure him quite easily.
Molly Cunningham from TaleSpin. If you ever piss her off, don't let her anywhere near your shins.
6teen's Nikki Wong maybe the smallest member of her group, but she is by far the strongest.
Kim Possible: Pretty teenage girl, cheerleader and scourge of supervillains, for whom kicking henchman ass is a hobby. Also her sidekick Ron's adopted little sister, Hana is a toddler with prophesied "monkey ninja" powers.
To get an idea of how powerful she is, the episode "Fall Weather Friends" featured a strength contest between her and Rainbow Dash at one point. RD manages to simply hit the bell on the strength-test machine. Applejack? Thanks to years of applebucking practice, she completely destroys it. And Rainbow Dash herself isn't that bad. In the hoof-wrestling part she easily won over Applejack.
Also, seeming fragile flower Rarity, who, when forced into a fight, hardly relies on her magic at all and is far from helpless in combat. This includes straight out punching out a Mook or two at one point. Heck, in the pilot, she kicks a manticore in the face.
Really, any pony at all who can kick ass is this. It goes with the territory. Equestria does seem to have something along the lines of a military composed of brightly-coloured ponies.
Mabel from Gravity Falls is undeniably cute and packs a mean punch.
Isabella from Phineas and Ferb is very cute but also very tough. Also, she is not afraid to use said cuteness as a weapon, as shown in "Meapless in Seattle".
Yin and Yang for Yin Yang Yo! are two cute, technicolor rabbit twins who fare pretty well despite their small statures. Yang who uses might, thus relying more on his strength certainly qualifies although Yin proves more than once she doesn't always need magic to fight.
Stitch from Lilo & Stitch looks like a blue koala and can singlehandedly take down enemies twice his size (It helps that he can lift 3000 times his weight). His preferred weapons are his fists and his jaw.