1) Be patient. Believe it or not, Ganon is actually terrified of you. A whiffed L-cancel means dying, a predicted roll means dying, getting crossed up when you aerial can mean getting grabbed and dying. So even though he can punch your face off without a lot of trouble, he is highly unlikely to get in your grill; this gives you room to learn his patterns and condition him as much as possible.
2) Read his movement. Ganon is heavily reliant on things like wavelands, double jump, and fast-fall fake outs to lure players into his range.
3) Don't go above him. Don't go above him. Don't go above him. Don't go above him. Don't go above him. Don't go above him. Don't go above him. Don't go above him. Don't go above him. Don't go above him. Don't go above him. Don't go above him. Don't go above him. Don't go above him. Don't go above him. Don't go above him. Don't go above him. Don't go above him. Don't go above him. Don't go above him. Don't go above him. Don't go above him. Don't go above him. Don't go above him. Don't go above him.
4) Don't rely on d-smash. Use f-smash more often, because if he happens to short hop an aerial it gives you a MUCH larger chance of hitting. If he fast-falls while getting hit, it utterly ruins his day.
5) Mix up your wavedash spacing as much as possible. He NEEDS to get complacent and fall into range of your movement and attacks without realizing it. If he looks like he's going to b-air, it's very possible that you can actually slide UNDER him, avoid the move, and grab on landing; however, you cannot allow him to actually perceive this sort of thing is going to happen to him.
6) Make him miss as many aerials as you can. Put him under the illusion that he is failing to hit you and it will make him uneasy and impatient.
7) Do your best not to get caught at the edge of the stage while he's on the ground, because his forward+b ***** your shield and if he pushes you to the edge you are in a terrible, terrible position.
8) He can jump out of the d-throw CG once he hits something like 40-ish? If Ganon DIs in he should be able to double jump out. Maybe I was just screwing it up but this is what happened to me.
9) Edgeguarding Ganon is deceptively difficult for ICs because Nana ruins your normal strategy. I wanted to start trying my up+b cancels right before Ganon can himself up+b, to keep Nana out of range of his grab, but I didn't realize this until the middle of my match vs. Iori and I couldn't exactly stop to experiment.
10) You can gain occasional safe damage on him by using sync'ed forward+b, and the boost to your horizontal momentum is significant enough that it will take him by surprise used sparingly. It's a really weird strategy though and I haven't worked it out much, there are times you can get away with it and times you can't, and I can't really put it into words ATM. I'll think about it more. This is how I opened my set vs. Iori though, so that I could lay claim to some percent and force him to approach first.
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That's most of the stuff I learned. A lot of it is just pay absolute attention to his movement and don't get suckered in or you will lose Nana from one aerial.
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Edit: Do any of you fine gentleman know where I can get some images of the Black/White Mage ICs from the Melee texture hacks? They're ultra adorable and I'd like to set them as my avatar.
Double edit because it's too important to forget: RockCrock is ultra legit. Great guy who was willing to sit down and help me learn things about the matchup. Iori's alright but he paused by accident while I was infiniting him and I want to give him **** about it