As far as I can tell many of you are not familiar with GW at all heh.
He edgeguards with dair by slowfalling it. If you fastfall GW's dair it slows it down a considerable amount and just puts a giant slow moving hitbox out to edgeguard with. On top of this you can change the fall speed whenever you want so say if I run off dair I just go fast till I get to them and can slow it down to punish dodges etc. It prevents you from using FC for the most part, I mean it even goes through marths up-b when he's recovering. Full hopped and slowfalled you don't fall very far and can use your second jump to cover all horizontal recovery options that most characters have. GW is pretty much the best character in the game aside from MK at edgeguarding MK(the hardest character in the game to edgeguard obviously) and that is mostly because of dair.
Now you're thinking "well we should be recovering high". No you shouldn't. GW is at his strongest against any character in the game when they are above him. GW controls vertical space far better than any other character due to his massive wind boxes on uair which lead to wasting jumps, frame traps, refreshing moves, combos, kills, etc. And guess what happens after GW gets a hit in? You get sent above him again. The best way to recover against GW is to try to get to the ledge safely. Recovering above the stage and landing on it basically isn't even an option considering how much GW players want you to do that.
Now, for the sake of people not just taking my word for GW beating kirby badly let's compare their movesets etc.
Pretty much all of GW's moves are disjointed and out prioritize and range kirbys moves. GW's bair and dair are very punishable if used as an approach but also very useful if used as a follow-up or frame trap.
Now look at the godly move that is GW's nair. 17% fresh, multiple hitboxes, combos into itself, and beat kirbys entire moveset. Seriously, you can try fsmashing GW's nair while he's facing away from you and you will be hit out of it. It autocancels and is not easy to punish at all. This move alone makes GW very hard to deal with for a good amount of characters(mainly lower tiered ones). You'll find the characters that shut down GW have easy ways to deal with this(MK's fair/upb/nado, Snakes shield into ftilt, motor slide, or just nades, diddys nanas, marths range and oos options, olimars pivot grab).
Aside from that you have dtilt, which hits kirby out of all aerials and can only really be punished by kirby by running powershield which is very telegraphed. This is a good follow up for dthrow as it will sometimes combo even if you tech. Gw's jabs interrupt all of kirbys moves and are great for getting grabs. Gw's fair beats all of kirbys moves in the air/ground and is really good to use OOS because it's guaranteed a lot making it hard to punish. It's also great for edgeguarding with high knockback when sweetspotted.
What does kirby do then? Kirbys zones. That's about it. If the GW is being silly and approching with bair/dair then just grab him all day lol but if they are smart and using bair cancels as approaching with nair/dtilt/crossupbairs etc then you will find yourself having a lot of trouble so you just want to bait moves and punish with bair, or maybe some fast tilts if you get to the ground. Condition for dodges for kills, pay attention to stage control, it doesn't do any good to hit GW with fsmash at 150% if he flys across FD because he will just BB it. After you fthrow uair at low %'s GW will always up-b away and cancel it into a fast fall. This is punishable but if he still has hit jump it's really not since GW can jump after using his up-b. Try to keep a lead and force approches, always doing retreating moves unless you have a guaranteed hit. Don't attack GW's shield unless it's with bair and you are running away after lol.
That's all I have for now I guess.