Ivysaur and Charizard both do alright with platforms (Ivysaur gets a nice aerial wall and Charizard gets super-safe Flamethrower). They have the range to keep Dedede from getting in, they both edgeguard him well, and they both can do a lot of damage within a few hits. Ivysaur can't do much damage without putting herself at great risk, though, and Dedede lives much longer, obviously. Also, if you think taking a stock from Ivysaur is as simple as getting a grab, I can tell you now that you're wrong. Dedede gimps Ivysaur with a hard read at the edge, but not much else. Ivysaur B-Air outranges all of Dedede's edgeguarding methods, and you have to guess exactly when Ivysaur will use her double-jump in order to prevent her from getting to the ledge.
Squirtle ends up doing okay against Dedede. He's sort of like Wario, except his ground game allows him to compete on the ground with more than grab. Squirtle can camp Dedede quite hard with shellshift stuff, too. I'd say -1 Squirtle, -1 Charizard, -2 Ivysaur (on, like, not-Final Destination), and I'd average it as a -2.
