Here is the full list of all 9 Secret Santa achievements.
Finish the Halloween list
Complete Krampus mode
Light all hidden menorahs in the nice, naughty, krampus, and mars list.
Complete the mars list
Finish all levels featuring nog with dizzy santa
Complete the Krampus list
finish the Nice and Naughty list with all milk and cookies collected.
Complete the Naughty list.
Finish the Nice list