With Bravery being introduced, MCH is arguably the single biggest threat to anyone's Battle High level. A lot of people who play MCH are just @$$ with it, but you get a good player who can actually mouse-over targets and pick them out in a crowd; the thing is now an executioner if it wants you dead. Bravery actually gives Spite the impact of getting head-shotted by a sniper rifle in any FPS.
Naturally, the MCH's Battle High level is a factor in how much prep has to go into the target before Spite, but on most ranged dps/healers, an Analyzed Drill/Anchor/Chainsaw into Spite is probably a guaranteed kill absent of Guard or mitigations like shields. And it's no joke for melee either; I've seen a BH5 MNK get taken-out by a BH5 MCH's Spite after only getting the buffed chainsaw's defense break.
While this may have been true prior to the giant initial damage snapshot changes in 7.1(?)(where the crosshairs meant the damage had already been applied, and was waiting for the animation to resolve, meaning it was impossible to react with Guard to), after their changes to snapshotting various attacks creating damage delays (even with the toning-down of them in 7.2), Spite is reasonably reactable to with Guard, and is still your best defense against it. If it's hitting you even after your bubble is activated, it must be your own latency or you're reacting too late when the crosshair animation is about to vanish.