My pick for the worst Beatle - Paul. No contest here. Ive always been a big Lennon fan, and I like a lot of Harrisons stuff too.
IMO, it was after the Beatles that it really showed who was the best musician. John made great music, so did Harrison. Paul never did anything good on his own, and what he did, I cant help but to think that he was always playing the Former Beatle card in his solo career.