Fallen Avatar https://www.wowhead.com/spell=239132/rupture-realities dealing insane amount of damage. On Heroic mode it deals more damage than on mythic Retail.
Try to stay in same range on Heroic mode with 920-925 lvl character as on the video and you will be killed. On FK Method players have had average 930 ilvl. And the guy on video lost 2.2M HP on 35-40 yards range with vantus rune and atonement on him, so average damage on retail without any buffs and versality is around ~2.8M on mythic. On Firestorm it Deals 4M+ dmg in heroic mode on 40-45 yards range.