New Assassin Item Nightfall Passive Damage Spreadsheet.
I made this to bring some clarity to the numbers this passive will actually put out, this spreadsheet shows the damage it does at 3 health ranges, with various physical damage reduce numbers.
Obviously 20% is going to be no armor targets and the item wielder will have a ton of armor penetration, 40-50% is going to be your average ADC, 60+ will be a heavy armor tank. There is enough info here to infer damage to 5k+ hp tanks, and almost any range in between when using your head.
Some of these HP ranges and armor amounts should never be met, but they're there just because.
https://docs.google.com/spreadsheets/d/1_yI4GRWHwzufHgiBJKb8jeQiWXeUztk_-mRfsoP4Weo/pubhtml
As you can see in this spreadsheet...it's not killing anyone who isn't pretty much dead already, it is not as strong as a zed ult, or even a thunderlord's decree until the enemy has a LOT of health.