Last Christmas - That is absolutely, hands down my LEAST favorite Christmas song of all time. Every time I hear it I just cringe. I mean it's just awful!
I really hate Jessica Simpson's remake of
I Saw Mommy Kissing Santa Clause, I think it sounds wh.ory.
I tend to like songs that sound more traditional. I really don't like hearing peppy annoying remakes of the older traditional songs. Andy Williams is/was my favorite singer of Christmas music. So sad he died.

Oh and I really don't like when pop stars (or Disney stars) try and make up new Christmas songs. I just want to slap them and say "you do NOT have the musical chops to be making your own Christmas songs so just STOP!"
Okay yeah, I'm a little opinionated about this stuff. It happens when every year some Christmas music starts shortly after Halloween instead of waiting til Thanksgiving.