I actually defeated Ur-Child

Party was Dark Hunter, Alchemist, Gunner, Hexer and Troubadour. I was supposed to use a link Order build by i somehow FORGOT to equip link order II on my Dark Hunter. My party was quite unoptimized compared to the setups you would find in YouTube and gamefaqs, but i somehow won with the Very simple strategy of Burst Shot + Cocytus Formula buffed by Frost Fantasia, Compression, Reverb, Draconic Fury and Ice Prelude, and Snake Eyes to debuffs the boss. Basically i Just stacked multipliers to do big damage numbers and called It a day, was not expecting It to be that effective.