Can Pawn Sacrifice deal 6 damage to a single creature?
No, it cannot deal 6 damage to a single creature. Here's the response from Brad Andres (developer at FFG):


  The second instance of damage does indeed “fizzle” because pawn
  sacrifice indicates with the “each to 2 creatures” phrase that you
  must choose 2 creatures and not the same creature twice. Hope that
  helps!