Welcome to The Cave of Dragonflies forums, where the smallest bugs live alongside the strongest dragons.
Guests are not able to post messages or even read certain areas of the forums. Now, that's boring, don't you think? Registration, on the other hand, is simple, completely free of charge, and does not require you to give out any personal information at all. As soon as you register, you can take part in some of the happy fun things at the forums such as posting messages, voting in polls, sending private messages to people and being told that this is where we drink tea and eat cod.
Of course I'm not forcing you to do anything if you don't want to, but seriously, what have you got to lose? Five seconds of your life?
There's plenty of possibilities, but probably what comes to mind for most people is a Kecleon riding on top of a giant Bronzong. Kecleon shoots Flamethrowers, Ice Beams and Thunderbolts at you while Bronzong shields him and uses Earthquake!
You have to shoot Bronzong's eyes with Light Arrows to daze it, then go Morph Ball and drop a Power Bomb underneath it to knock it down. Then you have to hit Kecleon with a Plasmid of the appropriate element, because he keeps changing his type! Rinse and repeat until a tragic cutscene triggers, in which you have to shoot Kecleon while Snake Eater plays in the background. (He was your best friend.)
You can also bypass this boss fight entirely if your Speech skill is high enough.
Aegislash.
Start off by hitting it. It will do a roundhouse Sacred Sword attack and a ranged Flash Cannon. When it is down to 75%, it uses King's Shield and continues the Sacred Sword and Flash Cannon antics. When King's Shield drops, you have to knock it into fire pits around the arena. Those deal damage to Aegislash and make the fire pits temporarily disappear, and you attack it while it recharges King's Shield. At 50%, it summons Dusclops that fly around the arena. You have to hit Aegislash with the Shadow Balls the Dusclops shoot while King's Shield is down. At 25%, it does the beginning of the fight again, until it dies.