I definitely see Hoopa taking up this challenge since she's 4× weak to dark types and would be more boastful about taking bigger things in her ass due to her rings.
Either her or Lunala. If it's Hoopa, she probably loses from being smaller, and if it's Lunala it's probably from being less experienced.
Hoopa seems likely since she's introduced first
Hoopa would make sense sinse she's the first 4x on the list.
She might try and use her other form to make her ass biggerbut then lose after it takes away her love for anal
