1st phase for me was my A team haha, Warmaster made it trivial really.
2nd phase was my Prim led squad and this was a much more level playing field, I almost got wiped by his multi hits twice but I fortunately had Alfyn and Olberic left standing respectively to do full team revives. Legitimately thought I was wiped both times. Leghold Trap seriously saved my life here. Had to get rid of Lyblac first to stop the heals, then focused on the Maw. Here I got the first of my near death experiences but I got everyone back online to 3000hp and that idiot Dark God just looked at me ominously instead of finishing me off. Once the maw fell I had to deal with a hyper powered sword arm which scared the shit out of me whenever it got it's one chance to double turn recover. Once Galdera was alone it was smooth sailing, finished him off the only way I know how - AMPUTATION!
This was Bizarro Sephiroth but actually well done instead of being totally confusing. A very worthy final boss that was so satisfying to fight.