KK post
The main things that Ganons do are
1) jump back (or stationary) Fair
2) jump back (or stationary) Bair
3) Fair, Uair, or up-angled F-tilt when you're above them
4) F-tilt or Jab when you're ground level with them
5) Dair if you're below them
1 and 5 are countered by jumping and doing moves.
2 is tricky, you have to either go over it, under it, or make them turn around with needles. It's sort of hard to DD grab because they can SH Bair and then immediately DJ, and the SHFF Bair autocancels so there's not much lag.
3 is countered by not being above them. There's not much advantage to being above Ganon, if there is an advantage there at all. So don't be there.
4 is countered by DD grab.
So basically all you have to do is camp and DD when you're grounded and close to them (don't get too close) and jump at them when they jump back to do really, really slow moves. Don't run into their moves.
If they're approaching you, your ground movement and faster startup will win the matchup.
Duck goes under his grab, Jab, non-low F-tilts, F-smash, D-smash, U-smash. So abuse that when you're both grounded. Ganons will likely low their F-tilts (or use D-tilts) to counter this but then they sacrifice the range of the F-tilt to do that and the D-tilt is laggy so you just have to keep outside that range and your duck will be safe provided you can react to and handle Side B, Down B, and Up+B shenanigans.
If you're close to them in shield, crouch is very good. However, beware of Up+B OoS, it's much faster and more ranged than you think it is. However, nobody does it.
If it's an option, combo into grab and chain grab. If you have the chance to combo with D-tilt or D-smash, consider if you could grab instead. If so, do it and chain grab them with no remorse.