Emily or Hanna is -A. I'm calling it now.
Think about it.
Emily and Hanna have the most reasoning, in my opinion, Emily more so. The first note Ali gets reads, “Its My Turn To Torture You.” Alison tortured Emily, she made Em fall in love with her only to reveal she truly didn’t love Emily back at all. Scorned lovers are the most dangerous people in the world, because they have nothing left. When Ali came back, Emily ended up being the angriest, because she let Alison play her again. I just feel like Emily could easily have the motive, and that it would be obvious since season 1. On top of that, Emily has had the least amount of bad things happen to her. People always say Maya was killed by -A…she wasn’t. She was killed by Nate. Theres no correlation between Nate and -A.
In fact, -A helps Em. For example, telling everyone Em was gay in S1. She ended up not having to tell her family herself. It helped her, in the end. I just truly believe Emily has the motive and there is certainly evidence against her.
As for Hanna, I’ve seen amazing theories (including a theory that her and Ali are twins which is AMAZING) and I honestly feel like after Emily she has the most motive. Alison taught Hanna HOW to hurt herself, and out of all the girls, I feel like we know the least about Hanna. Hanna could easily have other backstories, other things we have no clue about.