I don't believe there is a definitive "worst" Christmas song, but there are certainly some that are less popular or have become outdated over time. Some examples might include "The Chipmunk Song" by David Seville, "Grandma Got Run Over by a Reindeer" by Elmo & Patsy, or "Dominick the Donkey" by Lou Monte. These songs have become synonymous with being silly or gimmicky, and they are often avoided by serious Christmas music fans.