Bill would obviously win but I love herobrine in Alan's animations.

WAIT I DIDN'T SEE CHARA NOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOO

Either Herobrine or Shadow Queen, Bill doesn't possess people for any reason other than to access the real world (and fun), Frisk has no resistances to physical attacks, and SCP 035 can still be defeated if you destroy the body entirely.

To be clear, this is SPECIFICALLY when they're possessing someone and not in their base forms.

If Bill was in Dipper's body during a fight, he'd be nothing against AvM Herobrine

Chara can just reload if they die

Didn’t Bill get defeated by being tickled?