Worst singing accent? Wouldn't that imply that the singer was singing in a manner unlike she/he would normally speak? If so, I'd have to nominate the dearly departed hysterically comical character of Inspector Clouseauuuuuuuuuu (Peter Sellers) when he was singing "Thank Heavens For Little Girls" to the Russian Spy who could not, for the life of her, figure out why he just didn't seem the same as when she fell in love with him--or who she thought was him but instead was Omar Sharif in the dark.