Arya Stark was one of my favorite characters in the show. She's the youngest daughter of Lord Eddard Stark and Lady Catelyn Stark (Tully) but the most tomboyish by far. She's also the closest Stark child is to Jon Snow, as both of them always felt like the black sheep of the family. She wants to be a fighter early on, to which her father Ned Stark doesn't approve.
But he does hire a skilled swordsman to be her "dancing teacher" so she could be happy. While her training her didn't seem to help her much, I liked how Syrio Forel died to protect her. Though he had the chance to take a fallen metal sword. Never understood the logic there.
She's there when Ned Stark loses his head. I thought this added well to the drama, though a man of the Night's Watch prevents her from actually seeing the carnage.
And he tries to get her back to Winterfell by making her act like a boy recruited for the Night's Watch. That's where she meets Gendry, King Robert Baratheon's bastard son. It is kind of neat that their fathers were best friends and they happened to meet by fate. Though King Robert had a lot of them, so maybe that's just mild luck.
But instead of going to Winterfell she ends up almost being caught by the Lannisters. I liked her scenes with Tywin (whom thought she was a "common" Northern girl), it was fun to see the two of them bond in a way.
But she ends up later with the Hound, in a fun adventure across Westeros. And by fun, I mean funny. Doesn't work out too well for Sandor Clegane as Brienne of Tarth defeats him and almost kills him.
She ends up going to Braavos to become a "Faceless Man" at the House of Black and White. A religious cult of sorts, but it did teach Arya (bitterly and painfully) how to be a great assassin and face-changer.
I think most people loved when she took out Walder Frey and his house at the Twins, the very sight of the Red Wedding. That's where most of her cool assassin stuff ends.
As she's more of a soldier defending her home when the Night King comes. I did scream in joy when she turned him into chunks of frost. I didn't see her being the one.
But everything after that was disappointing. She should have been the one to kill Cersei Lannister and/or Daenerys Targaryen but she kind of passes it all up. Leaving that job to bricks, and Jon Snow's dagger.
At the end of the series, she leaves the country and sails far west. Probably reaching George R. R. Martin's version of the Americas. Makes me wonder if the books will hold the same fate for her or not.