The thing with the Whisper is that its shots have the ability to overpenetrate targets, and I think Bungie may have overlooked how this perk affects the triggering of White Nail. I haven't done extensive testing or anything but I believe this is what's happening: - You headshot a target, the game registers +1 to its crit counter for White Nail, BUT, the shot overpentrates and either hits a different part of the target, hits a target behind it, or hits a wall, the ground, etc...at which point a non-crit/missed shot is registered and resets the White Nail crit counter to 0 This can even work to your advantage if you align your targets correctly. I have triggered White Nail with 2 shots against a tank (easy since their crit spots are lined up pretty well) - 1st shot overpenetrated to the crit spot behind it, registering 2 crit hits, and my 2nd shot to a different crit area triggered White Nail. Theoretically, this means you could pop off 1 shot through 3 targets and proc White Nail if each hit is a crit. This not only affects White Nail, but Mulligan as well! Pretty much no downside though, as bullets that overpenetrate and get logged as a miss have a chance to give back ammo, nothing bad about that. You do damage, AND get your shot back. The problem is that Overpenetration doesn't happen 100% of the time, so, you can't plan for it to work for or against you at any time. What Bungie needs to do is adjust things so that Overpenetrated shots don't affect White Nail negatively. If someone can pull off multiple overpenetrated headshots with 1 bullet, then they deserve a White Nail reload for that, but if the overpenetrated shot misses, it shouldn't reset progress toward the triggering of White Nail.

Use Valkyrie to stun Xol first.

It works most of the time. There are certain criteria that won't trigger it.