For this trophy, the final battle is a three part fight, you only need to 5-star the third fight. The team I used was Fan/Hope/Lightning. Stage 9 of their main roles were maxed out and no CP was used on second roles.
Fang was equipped with a maxed out Venus Gospel, a maxed out black belt, a level 1 speed sash, and the cherub crown.
Hope was equipped with a maxed out Eagletalon, a maxed out black belt, level 1 sprint shoes, and a level 1 blessed talisman.
Lightning was equipped with a maxed out Enkindler blade, a maxed out black belt, level 1 sprint shoes, and the growth egg.
With Fang having the Venus Gospel she will have the stagger lock ability which will keep her from putting Orphan, or any other enemy, into stagger. With the Speed sash, along with the Venus Gospel, Fang will have the Instant Random Chain (IRC) ability which has a chance of putting Orphan right at the stagger point the more hits she makes on the target, Hope or Lightning will have to actually stagger Orphan.
When you get to this fight, start out in Com/Rav/Rav and use that for about three or four turns, the stagger bar will begin to fill rather quickly, then switch to Sab/Syn/Med and stick Deprotect, Deshell, and Imperil on Orphan, then switch to Com/Rav/Com and you should be able to take Orphan out before the stagger bar completely depletes.
My target battle time was 2:20, I completed this fight in 1:16 for the 5 star ranking and the trophy.