having a hard time trying to complete this challenge my Team atm is Omni Rize lead Omni Izuna Omni Lara Omni Daze and 7 star Marieala Other unit are omni kuyluk, omni holia, omni johann, omni hisui, 7 shura, glen, eleanor, lanza, licht, gyras, sonia, serge, stein, malef, rozalia, gregor, garrel and lyonesse
HC Boosting lead + Zelnite Friend + High Hit Count units. Go on a quest with lots of battles and single target attack everyone down. This is probably the easiest way to finish the quest.