It's like this.....
If we're talking about before Eric and Junior were "dumbed down":
1. Eric
2. Junior
3. Cole
4. Kel
5. Waldo
If we're talking about AFTER Eric and Junior were dumbed down:
1. Eric
2. Cole
3. Kel
4. Waldo
5. Junior
Before Eric was dumbed down, he was just your average teen white boy who liked girls, clowning his little brother and being funny. After his change, he just started acting like a doofus around people.....however, he was never really 'dumb' because he still knew how to be serious and talk sense when the situation called for it, e.g. when the gang almost broke up over the prank war....so he still tops the list either way
Now Junior, on the other hand......THEY fukkED JUNIOR'S BRAIN UP LIKE I'VE NEVER SEEN BEFORE FOR ANY OTHER TV CHARACTER IN HISTORY
Junior was your average black teen in the beginning.....then they made him the king of retards

. He would get confused with the most basic shyt and couldn't handle the simplest shyt, plus he acted like a doofus (not just 'acting' like Eric's character who did it to get attention and entertain others around him, but rather that's how Junior really was)