She-Ra: Princess of Power has the title character, as well as Huntara, a purple-skinned Grace Jones lookalike who has no powers except a bunch of really cool weapons, but held her own against She-Ra in a one-on-one fight.
In fact, most of the women in the show were Action Girls, and the guys were the James Bondage types. Understandable since the show was created as the girl's version of He Man and The Masters of The Universe.
Avatars Kyoshi and Yangchen seemed to have been quite the Action Girls themselves. Especially Kyoshi, who split a fucking island in two during a battle.
Chief Lin Bei Fong: Head of Republic City police, metal bender and Toph's daughter.
Korra also has Asami Sato, a continuation of the Avatar 'verse's Badass Normal tradition. She's a polite young lady living in Republic City, and has had extensive self-defense training.
Kim Possible beats up super-villains for kicks, using only her cheerleading skills. She can do anything indeed.
The same goes for Teen Titans's Starfire and Raven.
Diana the Acrobat in Dungeons and Dragons. To a more subtle degree, also Sheila the Thief.
Candy from Dave the Barbarian. Sometimes parodied, sometimes played straight. Also Fang, Candy's much more aggressive younger sister.
Sara from Chaotic. Admittedly she looks like the Faux Action Girl for most of the first season, and is quickly defeated in the first battle she has, the first battle of hers that the viewer actually SEES is one of the most intense combats in the series up to that point.
Some female creatures on the show also provide examples, such as Intress, Laarina, and Takinom.
Cera from The Land Before Time. Granted as a dinosaur, she lacks the attractive appearance, but you have to respect a girl who can shatter rocks with her head.
From ReBoot, all of the main female characters were more than capable of holding their own, though AndrAIa was the only one to be consistently in the fight. Dot and Mouse were more often used for their command and technical skills.
Jessica from Gormiti: The Lords of Nature Return, as she proves by single-handedly defeating the Big Bad's pet dragon and knocking down Orrore Profondo (the second strongest of the Volcano Gormiti)
Transformers Animated: Blackarachnia, Strika, Starscream's female clone and Sari, after she took a level in badass. Professor Princess might technically count, although she's more about the gadgets than actual combat. Arcee might have been one, but never got the chance.
Courtney from Total Drama Island definitely has Action Girl moments, such as ripping a lamppost off its base and hunting Harold down with it, and wrestling sharks in Total Drama Action.
And say what you will about Heather, but first season she definitely held her own in the more physical challenges. Though in the first season, she could also qualify for being a Dark Action Girl.
There's also Izzy, who gets into fights with a Scary Black Man twice her size.
Heck, all the original female contestants except Blaineley and Sadie.
Also, every female contestant on Revenge of the Island, except for Dawn and Staci, qualify as well.
Most of the major female characters on Phineas and Ferb get a chance to play Action Girl at some point or another. Recurring character Vanessa may be the best example, though Candace, Isabella and the other Fireside Girls get plenty too. (Candace once wrestled an alligator for an Achievement Patch. The very fact that this was an Achievement patch for preteen girls speaks volumes about the Fireside Girls.
Jem and her band were no strangers to action...neither were their rivals, the Misfits.
Arthur (animation): S14's "The Agent of Change" involves Francine, Muffy, and Molly creating a cartoon out of frustration with no good movies about female heroes. To top it off, they call her "Agent XX".