Note: In order to get the best ending you will need to get Shania's Tirawa final fusion and have all of her statues levels up to their max, level 5.
I begin the video at the final save spot in the inner sanctum of the Gate area and walk up the cliff side to the final battle area. It is here that you encounter Lady who summons the malice Umbral after she cannot revive killer at the altar. For the final battle I choose Mao, Frank, Johnny, and Ricardo because of their versatile moves and familiarity.
During this battle, I have my characters combo as much as possible on the Malice Umbral, having the final attack be one which takes away the bosses' stock if possible to prevent a double counter attack. The attacks that come to mind would be Mao's Sake cup Purge and Johnny's phone call move. In general this battle for the most part is getting your hits in on the Malice Umbral but also keeping its stock in check before it gets an attack turn on your party. I also found that Johnny can be conveniently moved around in the order or gain an extra turn by taking pictures of the bosses, which I needed anyway for the snap shot collection. In most instances you can maneuver him to be the last combatant in the battle order before the boss gets its turn. This is helpful because Johnny can utilize the phone call move to remove some stock from the bosses gauge.
Late in the battle, once the Malice Umbral falls Lady will unload on your party with an extra combo automatically. As seen in the video, one of my members fell because I was not expecting the out of sequence attack. At this point it really didn't matter though because Johnny is set up to assault her immediately. Once Johnny slams her in the head with his knife, cutting through her barrier, the battle is over and the ending begins.
I let the good ending play through at the end ending the journey with some credits near the end.