Paul McCartney - "Too Many People"
Disses: John Lennon & Yoko Ono
Shortly after the dissolution of the Beatles, Paul McCartney released two solo albums, McCartney and Ram. The latter, released in 1971, contained the charged "Too Many People," which chastised John Lennon for being a bit of an empty moralizer, claiming, "too many people preaching practices/don't let 'em tell you what you want to be" in response to John getting a bit preachy in the Beatles' waning days.
McCartney also mocks Lennon's decision to ostensibly choose Yoko Ono over his former band, with the refrain "you took your lucky break and broke it in two" suggesting that Lennon traded his shot at greatness in a singular, successful unit for the sake of romance and, secondarily, experimentation as a musical duo.
Though brief jabs, these lines (and "3 Legs" and "Dear Boy," other songs on Ram that Lennon perceived as slights) would awaken the ire of McCartney's former songwriting partner.