By far the simplest way to win, if you can manage it, is to just prevent him from ever taking a turn. You'd still need to ensure you permanently have shields on so he never counterattacks, but Valk can manage that, if she's booked. Obviously this requires a lot of turn meter reduction, so you'd need your Armiger fast, plus a Coldheart, ideally in Destroy set so after a while you can start killing him fast. SK could also be helpful because of the decrease speed debuff. Maneater helps with TM control as well, or Psylar. 

Ok, so I should go with arminger, coldheart, Valkyrie, Stag knight and psylar? 

Thx for advise, I hope arminger will be enough to bring in 🤔