I can't really choose a worst. But here's my best.
John = 1966, How I Won The War, with his glasses.
Paul = 1968/1969.
George = 1967, Sgt. Pepper.
Ringo = 1969, Abbey Road.
Love John in HIWTW. It's a shame because all of the images on the internet are either of him in full army gear, too dirty, too clean, without glasses or too low-quality. Hm.