Overview
In a nutshell
King Dedede is currently ranked 11th on the tier list due to his amazing chaingrab and powerful throws combined with an extensive grab range (this property alone got him to third place on the first tier list), his ability to perform Sacrificial KOs, a fantastic edge guard game, greatest resistance to vertical KOs (a combination of being the fourth heaviest character and having the fastest falling speed in the game), great range, good recovery for his weight class, good Waddle Dee Toss projectile blocking, a few quick, hard hitting attacks, and having what could be considered one of the best defensive games, which is made better by being one of the most difficult characters to KO in the game. King Dedede, however, suffers from a very large hitbox; combined with his 
falling speed, Dedede is ironically very easy to chaingrab, and this also causes him to be relatively easy to juggle and combo. His overall lack of speed also hampers him, with his only fast killer being his up tilt. King Dedede good matchups for characters under him, most notably an 8/8 matchup against Donkey Kong, but he has mixed matchups against higher tiers; while he has slight advantages against Snake, Marth and Wario, he has poor matchups against others, including an extremely 
1/8 against the Ice Climbers.