It's a difficult choice, but my personal two ng that gives me the dry heaves,'cos I've no liking for them, and they are invariably sung very badly by neophytes with a guitar needing serious tuning, are:
(1) Donna, Donna, bloody Donna.... boredom, always sung by young ladies with nylon-strung guitars, which they tune after being asked to do their floor spot.
(2) The Crow on The Cradle - equal boredom - used by every 'committed' singer giving us the benefit of his 20 years of misery...right?
My humble opinion, after 43 years experience of singing, playing and making some of my living in folk clubs.
I take rejection and criticism lightly,