My least favourite (ignoring Yellow Submarine) is Abbey Road, just doesn't feel like the Beatles.
I'm surprised by this judgement of Abbey Road. Actually, I think it was rather Abbey Road that was the 'new phase' Beatles album, rather than Let It Be. In the sense that if they had continued into the seventies, then they would have had that kind of excellent production. Abbey Road is a fine album, let down only by Maxwell's Silver Hammer and that annoying wind sound at the end of She's So Heavy.
I don't think they did a bad album as such. There are great Beatles songs on every album they did. Maybe Please Please Me would be the worst, in the sense that it was their first, and many bands worst albums are their least.