My early favorites are Paul, Leah, and Katherine.
Paul because he was in my survivor group game before in Croatia and came back for All-Stars. I think he is a dangerous player in the game. People might now see him as a huge threat, but when he makes it to the merge, Paul comes out of his shell and starts playing a strategic game, getting numbers. I'm afraid that he will be blindsided by his alliance tbh.
Leah because she was also in my survivor group game. She's an early favorite of mine because she will play a really good social game. I would be scared if I was to play with her in the same season because she's a really good social player.
Katherine because of her bitchy attitude, she'll be a queen even tho i hate her because she called be "the worst survivor host ever" like sit down miss! I think she will be a threat tho, they will see her as a threat in the beginning of the game. If she manage to get the right alliances i think she will further herself in the game.