A player with a Level 91 Barbarian has dealt what appears to be the highest damage number against Uber Lilith in Season 1 yet with a 
Rupture/
Caged Heart of The Barber hit that dealt 8,857,491,456 damage.
In the past, we covered a 100 billion damage crit, but that was only possible due to a bug. We also have a video of NathXplosion dealing the nearly 9 billion damage hiy linked below.