Christmas Evil/Don't Open Till Christmas

In Christmas Evil (1980), a toy factory worker, mentally scarred as a child upon learning Santa Claus is not real, suffers a nervous breakdown after being belittled at work, and embarks on a Yuletide killing spree. In Don't Open Till Christmas (1984), somebody with very little Christmas spirit is killing anyone in a Santa suit one London holiday season, and Scotland Yard has to stop him before he makes his exploits an annual tradition.