Hi guys - I'm a Luigi main who's decided that Pokemon are awesome... And I feet that I should comment on a few things.
With regards to tcanter's comment on Ivysaur's B-air:
I also know that he can nado through it
Against a non-button-mashed neutral MK special, Ivysaur's B-air, at the tip, will first clank with the attack (and cancel it in its entirety) and second smack the annoyance for a few percent. Also, a B-air against MK's drill rush clanks with the attack (but doesn't cancel it) and, as far as I have seen, either removes the hitbox over the course of the clanking or shrinks it down to the point that it only surrounds MK himself (what I observed: B-air clanked with Drill Rush, drill rush continued past to Ivy's upper right side, MK was not in contact with Ivy, but Ivy was within range of what normally should have been MK's drill rush's vacuum - that area to his sides that sucks people into the attack).
Just a little testing I've done (a confirmation from a second party would be nice).
also razor leaf interrupts and hits metaknight at the beginning of mach tornado, and if mk starts the tornado from a reasonable distance and stays on the ground, since that means they aren't mashing B to improve priority.
also fsmash is quite nice when it lands, i'm not sure of whether it'll go through fairs and the like. something to look into.
The MK player can tap the B button once every half second and maintain the tornado's priority (initial priority - not button-mash-bonanza priority) and level height - just a note.
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Regarding Ivysaur vs. Meta Knight, I see no reason why a
perfectly spaced Ivy should ever lose to a MK. Ivy's B-air outranges and out-prioritizes MK's aerials, an MK approaching from above can be given some seeds to the face, and an MK approaching on the ground suffers again to Ivy's B-air (along with long range grabs and tilts). This assumes, of course, that MK doesn't have any absolutely ridiculous approaches that somehow can hit Ivysaur through her awesome B-air and bullet-seed range.
Given that no one can perfectly space indefinitely, unfortunately, such a match-up is not realistic (akin to Olimar's perfect camping vs. Meta Knight). However, would it not be plausible to say that the closer one gets to perfection, the more winnable the match becomes?
My (slightly rhetorical) question: how good of a defensive Ivy would be required to push the match-up (utilizing the assumption I made earlier) to a 50-50?