Genaller
Silver Soul
True but that's only once it fully evolves into Decidueye which most likely is still going to be a while. So in terms of Ash being able to use the fighting type Z-move not to long after he gets the crystal for it he will either need Pikachu to learn Brick Break, Reversal( Egg move), Rock Smash, Focus Punch, Dynamic Punch, Seismic Toss, Counter, or Submission which the latter 6 transfer moves, or the Litten Ash catches will have to have it's egg move Revenge, or Ash will have to capture a fighting type pokemon, or at least catch a pokemon that knows a fighting type move otherwise it will be a while before he can use the Fighting type Z-move.
Crabrawler and Passimian are both probable canditates for Ash's team so he's covered there.