My mains are...
Captain Falcon, Ganondorf, Zelda, Snake, Link, Ike, Yoshi, Pikachu, Mario
Kirby's big keypoints from what I can see are his modal dashes, grabs, and standard aerial attacks (of course, the veterans here might disagree. Trust them more than this one if that is the case). If you can avoid those, you're halfway there.
Captain Falcon: Your Down-B on the ground makes for a decent approach, as does his dash. Watch out for the Cutter's Wave, though. Side-B can potentially get around that, but it's a toughie. U-air makes for good juggling and punishment follow-up if you can connect with that Side-B on the ground, but don't give 'em enough time to drop a Down-B on you, lest you wish to become Space Falcon.
Ganondorf: Side-B snatches Kirby out of the air, and is especially traumatizing as a short-hop attack. Getting Kirby over the edge and dropping a Wizard's Foot on his head works wonders.
Zelda: Nayru's Love in the air gives wonderful forward momentum, reflects his Cutter's Wave, has enough range to stop most of Kirby's attacks (sans the rarely-seen Hammer), and has low enough cooldown to follow up into other attacks such as her Lightning Kicks. F-tilts destroy a lot of Kirby's approach game. I usually try to knock him into range of Zelda's extended smash hitboxes.
Snake: I see little-to-no Snake play, but I would say setting up mines with the D-smashes and down-B. It's a gamble, but it forces Kirby to be more aerial, and his aerial approach is a bit predictable. Of course, his Cutter Wave might be able to get rid of your smash mines... I'm not sure, I'd have to check.
Link: Boomerangs. Boomerangs for days. That and Arrows. Lock 'em with a boomerang, then blast 'em away with a well-placed arrow or charged Spin Attack.
Ike: Ike has enough armor during his Aether attack that if you can land near Kirby and have your No Sympathy mode built up, a well-placed Eruption blows him up and away. Use Aerial side-B to approach (or as I call it, the
Poor-Man's Sonic)
Yoshi: Eggs? I don't know. Our Yoshi main kind of left.
Pikachu: B-Air makes for lovely approaches, as does Skull Bash and Quick Attack. Thunder CAN shut Kirby down on the edges, but given his control in the air, it's not as worth it as a well-placed Thunder Jolt or n-Air. Lock Kirby in the air with f-airs and b-airs, finish with n-air, or lock as much as you can with Thunder Jolt.
Mario: His Cape and FLUUD are going to be your best friends. Side-B turns his Dash completely around, and with its cooldown you can follow up easily with your own dash attacks or Firebrand. If you're edge-guarding, Kirby's Up-B is predictable enough that you can turn him around, making him miss the ledge completely and plummet to his doom (of course, from what I remember, 4.0 is gonna let Kirby grab the ledge from behind, so make use quickly). The Cape also reflects that cutter wave. As for the FLUUD, use that near the edge, then connect with spikes/meteor smashes, or let Kirby kill himself with his Stone attack. Alternatively, FLUUD brings Kirby to you to grab and back-throw, or just to wail on him.
