He might only have one wing, but Fafnir does his best to use his sheer size and limited hover ability against you (this might be a good time to remember that you can always change your battle camera in the Battle Menu). He's resistant to Non-Elemental, Fire, and Wind artes but weak to Water, so bring in Mikleo for the punch, and Edna for good measure since he is not resistant to Earth. Fafnir’s main attack has him hover in the air before slamming onto the ground - it’s difficult to break this attack, so your best options are to dodge, guard, or just get out of its area of effect. Be careful with your hidden artes - you don’t want to accidentally charge up his seraphic artes ‘Air Pressure’ and ‘Gravity Well’. Try to break these artes with your martial artes if you can. Thankfully, if he does successfully charge them, both artes only affect a small area at your current location, so you can dodge out of the way if you time it right. At lower health he starts to use the hidden arte “Gravity Press” and seraphic arte “Sinister Soul” - these artes are more powerful, but just use the same tactics as before to deal with them: break if you can, otherwise dodge.
Because of Fanfir’s love for seraphic and hard-to-break hidden artes, armatization is not very useful as an offensive strategy; if you do use it offensively, Mikleo armatized’s long distance attacks can take advantage of his elemental weakness while also remaining out of his arte’s reach, just remember to avoid accidentally charging his seraphic artes with your armatized hidden artes. Speaking of his weakness to Water, Fafnir can be inflicted with stagger or stun status quite easily, so be ready to go all out.
