King Dedede is a denizen from Dream Land, and one of the core members of Team Mario.
Much like Luigi, Dedede's personality develops over the course of the series. Initially depicted as self-centered, arrogant and greedy, Dedede developed a softer side after meeting Kirby. He was also shown to be rather cowardly; though not as much as Luigi; hiding behind Kirby or running in feat once things take a heavy turn. He was nonetheless a capable fighter and a skilled user of melee weapons, including spears, axes, and his trademark hammer.
After his arrival in the Mushroom Kingdom and following the defeat of Mecha Sonic, Dedede became calmer, and became less of a foolish arrogant hothead after being made leader of Princess Peach's new Royal Guard, though he still acted self-centered at times.
At some point following the defeat of Bowser and Smithy in space, Dedede gained a general interest in robotics, and picked up the tendency to label things he enjoyed as "super". His soft spot got considerably worse, however, as he would cry if he heard a sad or joyful story.
His bonds with the rest of the team deepened over the course of the series. During the high speed race between Team Mario and the roboticised Babylon Rogues, Kirby allowed him to race using his own Warpstar, whereas Kirby decided to race using the assembled Dragoon. After Kirby "won" the race, the two raised their fists at each other in respect.
During Kirby's battle with the Nocturnus Clan's Overmind, Dedede took a direct hit meant for Kirby, saving the latter's life, almost at the cost of his own. Dedede was also willing to put Meta Knight's plan to push back Yūrei's Birdcage, showing a great deal of trust in his former subordinate.
During the Super Shadow Queen Saga, Dedede became something of a father figure and commander to the team, being the one to decide to split the group up to chase after Beldam's Majins, and later, attempting to buy time for Sonic and Shadw to master the Fusion Dance. Despite Geno's dip into the realms of darkness, Dedede was willing to overlook this for the fact that he was planning on sacrificing himself for the benefit of others.