Worst because it's hackneyed must be that one about the female highway robber or John Barleycorn.
Greensleeves! syrupy tune and nauseating words. Not a folk song, couldn't be.
But the most irritating must be "The Day We Went To Blackpool" (or is is Brighton) Once you've heard that tune you can't clear it. It's put me off cider for life.
DocJ