The Jack Frost Persona is one of the easiest and earliest ones that a player can obtain or even fuse for in the games. For this purpose, I am going to use Persona 5 as an example since it is the most recent mainline game in the series with fusion elements to it. In Persona 5 and Royal, there are nearly 30 different combinations of Personas that you can fuse to make Jack Frost as early as the second dungeon in the game. However, my personal recommendation is to combine Silky and Mandrake together or Succubus and Pixie together as they are some of the earliest Personas that you can obtain relatively quickly.