heh, Metaknight and dedede arent really bad guys.
"Even if he has antagonistic qualities, he seems to be a guardian of Dreamland much akin to Kirby. Indeed, he has even come to Kirby's aid in more than one occasion which brings to question his motives and beliefs. It could be thought that when Meta Knight fights Kirby he is not necessarily trying to stop him, but rather test Kirby's skill, determination, and courage. Perhaps it is because he wishes to ally only with one who is worthy? Perhaps it is to prepare Kirby for the challenges to come? At any rate, he is certainly not an "evil" character." - From T!mmys metaknight thread
lthough he is not necessarily evil, he causes many problems for the inhabitants of Dream Land through selfish mischief, such as stealing their food or building a castle on top of the Fountain Of Dreams, so that the denizens suffer from dreamless sleep. His more heinous actions are more often due to possession by more sinister entity of Dark Matter, along with the rest of the usual franchise enemies. Despite this, he and Kirby have teamed up on occasions with the purpose of taking down a greater common foe.
King dedede is just a mischieveous self proclaimed king of dream land... he only fights kirby because kirby wants to stop dededes actions like stealing food or building his castle on the fountain of dreams. I think hell help the good guys take down the sse because it cramps his style of ruling and not following anyone, and their a greater foe like he has helped take down before