9. Skye/Daisy (Marvel's Agents Of S.H.I.E.L.D)
If there is one genuinely worthwhile thing the otherwise kind of mediocre Agents Of S.H.I.E.L.D brought us, it was the journey of Daisy from flighty hacker to unstoppable superheroine.
When we first meet Daisy, she goes by the name Skye and is a VERY different kind of character from where she is right now. Not only is her personality VASTLY different from where she ends up in later seasons, her role is much less defined and kinda redundant. After all, Fitz and Simmons handle the tech stuff just fine, so there's really no need for her hacking skills.
Then season 2 rolled around, and keeping with it being the best season in the show, one of the best twists in the story is revealed: Skye's real name is Daisy and she is an inhuman. While Grant Ward turning out to be a Hydra agent becomes clear if you know what signs to look for, this came right out of left field in the best way.
Daisy started the show with not having a lot to actually do or contribute to the team, and now she's easily the most important member. Which is the kind of reversal we can all get behind.