Some feats from Mass Attack that I'm trying to work in.
You know how they say that "at your weakest, you end up showing more strength"? Kirby is no different, with many of his most solid feats being shown at a time he had most of his size and power taken away.
Though the clips used show multiple mini-Kirbys working together, it's entirely possible to achieve these feats with just a single mini-Kirby.
While in space, is capable of out-swimming or even fighting off a creature that can create black holes. Yes, this one is 100% confirmed.
Catches and tosses away a large bolder spat at him by a mountain-sized monster.
Destroys large volcanic boulders with a few headbutts. I have no clue why they move so slow.
Performs body slams so powerful that they break through several layers of metal.
Shot out of a cannon so fast that he blasts through several layers of metal. Is perfectly fine afterwards. For doubters, another Kirby game specifically cited this as a durability feat.
While on top of a tall forest tree, grabs a bird out of the sky and slams it all the way to the ground. Kirby is fine afterwards.
Builds a fully-functional space ship, using it to fight other ships while powering through an asteroid belt. While it's possible for Kirby to collect blueprints to help him with the details, doing so is optional.
Uses himself as ammunition for a tank.