Hanala Jarva of the Uplifted series certainly qualifies. She is small, pretty and inexperienced. Yet she will not hesitate to kill anything that harms her crew, or her later lover Joachim Hoch. It's telling when a disenchanted Waffen SS Officer is the least violent member of the couple.
Paul of With Strings Attached always was known as the Cute Beatle. He doesn't look particularly strong either, having lost some weight during his “depression era.” But given that he once lifted an estimated 90 tons of solid rock statue....
The development of Terry Pratchett's female Assassins, who in the canon are at the moment nothing more than names, descriptions and cameo appearances. In Nature Studies, regard the slight, freckled and girlish Johanna Smith-Rhodes, who has a winning way with animals. To wit, the sort of venomous and generally dangerous fauna that would get her fan-mail from Steve Irwin. She also has a direct way of dealing with obstructive Palace Guards blocking her way to Vetinari. She teaches Natural Sciences, Zoology and Animal Management to student Assassins and has the capacity to organise some really interesting nature trails for her pupils, in which they learn that Nature is a thing to have wonder and respect for.
Elsewhere, the characters of assassins Miss Alice Band, Jocasta Wiggs, and Madame Deux-Epées are similarly expanded upon in the works of A.A. Pessimal.