Figured it's time to contribute
something to this boards.
So we had
this thread, which stopped updating. Reasonable enough; after all, there's a very large number of moves that will beat tornado (i.e. everything from above). So instead of going down and listing each move that will, let's instead just go over how to beat tornado.
Ignoring the scrawled numbers on this image, these are the hitbubbles for MK's tornado (the repeating part, anyways) made visible. They have various qualities; the upper ones hit at a 30-degree angle inwards, the bottom one straight up with different hitbox qualities if the opponent is grounded or aerial, they do one damage each and they repeat each frame. Also, they have normal priority (I'm fairly sure; it isn't transcendent like most of the rest of his moveset though).
Those last two bits are the only ones that matter. MK's tornado is so hard to beat because you basically can't hit it head-on. The hitboxes on the side will flat-out beat any hitbox that does less than 11 damage. If it doesn't do 11 damage or more and touches them before it hits MK, it won't break tornado.
You'll notice how there's that big fat weak spot on the top. If you're smart, you will very, very rarely be hit from above while tornadoing. Because the hitboxes aren't there, any move that hits you before it hits the hitbubbles will knock you out of the tornado.
However, if you want to beat tornado from the side, just doing 11 damage isn't enough. The hitboxes are massively disjointed. If you hit one of them with a hitbox that does 11 or more damage, if the MK is grounded you may get a clash animation (not sure about this one, I think it's happened to me once), otherwise nothing will happen (that particular hitbox will be broken, but it's replaced by another on the very next frame). In fact, if it isn't disjointed, then your hurtbox will fly right into the range of the next tornado hitbubble, and you'll be trapped. So if you want to assault it through the hitboxes, you not only need to do 11% or more, but you also need a disjoint long enough to hit MK's main body before the tornado hitboxes catch you. This is extremely hard for some characters (luigi comes to mind; he literally cannot beat tornado unless he attacks from the top).
EDIT:
So aerials will NEVER beat tornado, unless they hit from the top.
Transcendant-priority attacks don't interact with hitboxes. This is why falco's lazer and Diddy's bananas will always hit you out of tornado, as will MK's aerials. You don't need any particular damage with attacks like that, but you do need enough of a disjoint to hit through the hitboxes before they catch your hurtbox.
Bombs (TL's, Link's, nades) will interact with your hitbox and then explode. These, in the rule, have hitboxes that will not clash, and a fairly large explosion radius, so there's really no escaping them. Don't get hit by these. Stupid sexy snake.
TL;DR:
In order to beat tornado an attack must:
-hit from the top, avoiding the hitboxes altogether (dairs from the top, everyone has 'em)
-Do more than 11 damage with a considerably disjointed hitbox on the ground (example: marth fsmash)
-Have transcendent priority with a considerably disjointed hitbox/projectile/invincibility (example: Falco laser, diddy bananas, marth upB)
-be a projectile that explodes on contact with a hitbox (bombs and grenades)
In order to keep people from beating your tornado:
-stay above them with it. Don't just blindly tornado when someone is above you, you will usually be punished. If you want to blindly spam moves against people above you, that's what uair is for.
-Space and zone carefully with it if you know your opponent has long, powerful disjointed hitboxes and/or great mobility
-Never tornado a diddy who has a banana. It will not end well for you. Don't tornado into grenades either, it will similarly not end well for you.
EDIT: Worth noting that you cannot SDI tornado. No, really. SDI does not work on tornado. It has no hitlag, therefore you
cannot SDI out.
Most of this I figured out while hacking around on MK's tornado in PSA. Any comments/corrections/etc are welcome. Not the greatest help for
us, but someone might like it.