I’ve got 900+ damage amplified from Orisas ult twice now but I haven’t been awarded the spray.
This achievement is a little difficult to track in game. Remember the achievement requires the damage threshold in a single use of the ultimate. So if you are relying on post-game stats, that is not a clear indication if you used the ultimate more than once.
U have to do 900 damage but it only counts to amped damage so it does 50 percent damage boost so u have to do 2700 damage