One of the best aspects of Bambi II is evolving Disney's icon of cutesiness into a resourceful guardian for his herd, taking out an entire pack of hunting dogs by himself (bar one which is disposed of by the equally adorable Thumper and Flower).
The eponymous character of Coraline. A look that invokes Big Brother Instinct? Check. Underfed? Check. Having more balls than most healthy adult males? Um... check.
Emily from Corpse Bride is pretty cute for an animated corpse and proves just how badass she is during the finale in the church against Barkis Bittern.
It helps that Toothless takes some cues from Stitch from Lilo & Stitch. Stitch looks like an adorable blue koala with big eyes and can act as such, but he's also the 626th experiment created by an evil scientist with the primary function of destruction, and that trait WILL show if he feels the need, such as messing with his Ohana.
The Incredibles: Jack-Jack is a baby who can't even talk yet, but both Syndrome and the babysitter learn the kid won the Superpower Lottery, multiple times, with enough powers for a team in his own right.
Jack Skellington and Sally from The Nightmare Before Christmas. The former is one of the most adorable skeletons ever. He also is the scariest guy in town, and if you try to turn his friends into snake-and-spider stew, he will fuck you up. The latter is a sweetheart and also had the guts to go into Oogie Boogie's lair by herself to save Santa.
In the Shrek movies Puss-in-Boots takes serious advantage of this, weaponizing Puppy-Dog Eyes to catch opponents off guard.
The spinoff Puss in Boots introduces another Badass Adorable cat character by the name of Kitty Softpaws, who is skilled and tough on a level fit to rival Puss himself. And a literal "cat burglar."
Rapunzel of Tangled was fully capable of bringing down any of the thugs in the Snuggly Duckling with her all-purpose whip (i.e. her hair) and Frying Pan of Doom but she didn't have to. They were already subdued by her pretty, endearing, 'I have a dream' adorableness.
Morph on Treasure Planet. Seems like a cute, little blob reminiscent of Ditto, right? Not only is he capable of transforming into any given person or object (still remains the same size when in normal form), but can utter very snarky phrases like a parrot, and, when against Ax-Crazy Scroop, is able to put up a decent fight for several minutes. Badass Adorable, indeed.