Against vana with a fang on the last possible second of mask's cloak buff.
Though it doesn't do that 4 times, only something like 2 of the 4 fang hits actually pass 1k damage, while the others stay at 600, and yes, this was max damage.
Has anyone found the highest possible damage number you can actually get yet with the sprites around? I'm curious now.
http://forums.spiralknights.com/en/node/92288