nowadays Fact on playdota.com
"When Culling Blade is cast on a target below the threshold shown in the tooltip it will remove all buffs before dealing lethal damage to the target."
if you think of it its not often when buff removing is useful cause the target die in fact in most cases is useless but for shallow grave its working remove it and then is dealing lethal dmg possible to take down target or not? blade goes through magic immunity its fact but thanks this removing? just some question to forum its a very advanced mechanics so what you think of it?
Culling blade does 1000000 dmg, if the reQuirments are met, and shadow grave is ,IIRC ,hard coded heal, like void backtrack. But the target will still die if the damage dealt is greater then his total hp ex : void has 850hp, lina ulti him with agha - spell reduction, it will kill him nevertheless, no matter if backtrack would occur. Same for shadow grave.