The information in this thread is pretty sparse, so I’d like to add my input to this, if you guys don’t mind.
First of all, Kirby is a very combo-driven character. He is probably the best at stringing hits together next to Lucario and Diddy. The problem with his combos is that they’re damage dependant - they’re really only guarenteed when your opponent has low-damage; we’re talking 20% or less. The good news is that his combos can rack up damage quite easily doing at least 18% but as much as 50% or more.
Kirby has some strong hits to help finish off his opponents. His Forward Smash (F-smash) is a prime example. It routinely KOs around the 100% mark depending on the weight of your opponent and how close to the edge of the screen you are. His Up Smash (U-smash) can KO light characters around 90%, and heavier characters from 110% to 120%. His Down Smash (D-smash) is the weakest of them all. It’s best used either to KO light characters around 120% when sweet-spotting it (near his body), or as an edge-guard to knock an opponent horizontally to their doom (near his toes).
Kirby has two Special Attacks that are great at finishing off the opponent. The Stone (D-Speical) and the Hammer (F-Special).
The Stone is best used when you know your opponent is going to over extend their aerial attack from below. They think they might get that hit in first, or they’re using a long-reaching attack (like Marth’s sword), but you plummet down on their head dealing 18%. This can usually KO vertically around the 100% mark also. When used from the ground, Kirby’s Stone can still create a shockwave (like when it lands from the air), but it will only deal 14% and send the opponent in a horizontal direction.
Kirby’s Hammer can deal massive damage and is easily his strongest attack. On the ground it will deal 23% damage and send the opponent at a diagonal angle upward. The speed is slow, the reach is short, and the lag is bad, but that’s what you get with a 23% attack. Because of this, it’s best used ONLY when your opponent has left themselves so wide-open to attacks that hitting them is guarenteed. Instances include someone landing back on the stage after using their Up Special to recover (Marth, Peach, etc), a Jigglypuff who has fallen asleep, someone stunned after breaking their shield, etc.
The properties of Kirby’s Hammer when used in the air give you additional options! These include: faster start-up, aerial mobility back/forth, and a double-swing. Since the Aerial Hammer has obvious speed/mobility buffs, it makes a lot of sense that it is also much weaker. The first hit does 17% and the second swing can deal 15%. Don’t assume right away that the first hit is better simply because it deals more damage! Yes, it does 2% more damage, but it will send the opponent away in diagonal arc. The second swing will send the opponent away in an almost horizontal trajectory.
The ramifications of a horizontal trajectory can make big difference - it will send an opponent straight off the screen whereas someone being sent upward has more distance to travel and is more likely to surivive the hit. Additionally, many characters will have a much more difficult time returning to the stage from below than from above - coming down from above is like starting off with a free jump where coming from below uses up jumps and is easier to intercept.
Now, the truth of Kirby’s offensive faults should be obvious from what I have written. He can build up damage, but his main finishers are slow, laggy, or easy to see coming. This makes KOing inexperienced opponents a walk in the park, but against players of higher skill it can be difficult to find an opening to land a Smash attack, Hammer or Stone. You’re faced with the dilemma that if you launch a strong attack there’s a high probability of a good opponent seeing it coming and putting up a Shield or successfully Dodging. You will then leave yourself wide-open for a counter attack for a short amount of time - long enough for even a mediocre player to take advantage of with a variety of attacks.
To mitigate this fault, Kirby players will have to play an extremely patient game and will utilize attacks that don’t comprimise his defenses (weak attacks) while waiting for an opening to land a KO. Often times this will lead to the Kirby player relying on simply building damage from small hits until the opponent is off the stage and can be KO’d with aerial attacks.
Because of these tactics, Kirby is at odds against characters who either out-range him or do not leave themselves open when going offensive. A Kirby player will be unable to pressure his opponent with weak attacks if the opponent can out-do Kirby in offense. This will force a Kirby player to go defensive, getting fewer damage building attack in, and in turn will likely be the one taking the hits. Being a light-weight this is dangerous because most characters will not have to resort to using their strongest attacks to finish Kirby off.
Characters who are most dangerous to Kirby are the ones that have strong, long-reaching attacks with little lag. This includes Marth, Snake, Zelda and Mr. G&W. Meta Knight is perhaps the toughest match-up of them all because he is all about reach and speed which will completely beat out anything Kirby has, and even without powerhouse attacks he still has no problems finishing off Kirby.
Remember to work with your strengths and try to mitigate your weaknesses. Don’t leave yourself open, get your opponent off the stage, and maximize the damage you do stringing combos together.
Here are some useful combos to work with (remember, Kirby’s combos work best at 0 - 20%)
Basic Combos (only a little practice in Training Mode)
Vs. Floaties (e.g. Marth, Toon Link, Peach, etc)
Grab, D-throw, U-smash
U-tilt, B-air
D-air, F-smash (also works at higher percents if they don’t shield!)
Vs. Heavies/Fast Fallers (e.g. Bowser, Fox, Snake, Falcon, etc)
Grab, D-throw, U-tilt, U-tilt, B-air
Grab, F-throw, Grab, F-throw, F-smash
U-air, U-tilt, U-tilt, U-smash
Intermediate Combos
(a little practice in Training Mode, but also some experience in actual fights)
Vs. Floaties
Dashing Jump into U-air, U-tilt, B-air
F-throw, U-air, “reverse” U-tilt, B-air
F-air, D-tilt into Trip, Dash into Grab, D-throw, B-air
Vs. Heavies/Fast-Fallers
D-air, Dash into Grab, F-throw, up-angled F-smash
B-air, U-tilt, U-tilt, (full-jumped) B-air, Aerial Hammer
F-throw, U-air, F-throw, U-air, “reverse” U-tilt, B-air
Notes:
U = up, D = down, F = Foward, B = Backward, N = Neutral
All Aerial attacks are assumed Short-Hopped unless labled “full-jumped”.
Fast-Falling your attacks is based on your level of skill.