Sentsuizan (旋墜斬, lit. Whirling Crash Slash) is one of Zero's special moves in Marvel vs. Capcom 3. Zero charges forward with his sword downwards in a falling reap. It is a diving attack and can hit OTG.
At a fairly steep angle
Less steeper angle than M
Originally from Mega Man X6, Sentsuizan acts as a variation of Shippuga via its animation, where Zero in midair dives forward with sword extended and does a crashing Shippuuga attack upon landing; like with diving moves, this can cause unneeded suicides if used over a pit or any death spot, though Zero has invincibility frames until he lands on a solid surface.
In Tatsunoko vs. Capcom, its command was instead QCB + Attack in midair, and its OTG properties were not too strong as it does not pickup foes off the ground. However, it has quite a hitbox giving it a good amount of priority needed to beat out most standard anti-air normals. Usually the A/L version is great for all sorts of mindgames. It can also be steered left or right a bit to increase the steepness of the diving angles.
The move largely remains the same in MVC3, only it no longer has its steering property, and not until Ultimate it was possible to have a less steeper version via the M version. Its OTG property however, is a lot easier to make use of due to the tactics used to pop up the foe off the ground with a more easier lift boost, especially when powered up with Sougenmu (thus due to the second Sentsuizan from the clone, it's possible to cause a pseudo-ground bounce effect can be repeated in the same combo). And in Ultimate it's also possible to cancel it on-hit into a fully charged Hyper Zero Blaster to follow-up on the OTG, causing a lot of new combo routes with this move.
In Marvel vs. Capcom: Infinite however, this move can now be cancelled into a Hisuishou via releasing a max Hyper Zero Blaster charge during the animation.