Emblem Lord is pretty knowledgeable for strategies against Meta Knight, so if you are looking for something extremely detailed you should ask him, but here are some some strategies against Meta Knight:
- play defensively, camp if you have to
-SH fairing is always a good idea
- if he approaches with aerials, countering will make him think twice, if he goes in for a grab use your jab
- If he is off the stage and is close to the edge, jump off use a sweet spotted dolphin slash on him, then use your limited DI to get on the edge or stage. If you just try to fair him, if he doesn't hit the side, then he will very likely make it up again and possibly gimp you. But if he is at high percent fairing is totally acceptable to fair, or if he's relatively close.
- If you get knocked off and he tries to hit you with an aerial, just counter him
I am not one hundred percent certain with Dedede, but here is some strategies:
- since he's a big target, sh fair or nair works very well
- keep your range to avoid being chain grabbed
- if he goes off the stage use you fair like normal, he is an easy character to spike also.
- your dancing blade is effective against his bad mobility
- if he uses his up-b to get back on the stage, go under him and counter. He will catch on eventually and cancel the downward attack when he lands, but that's where you can punish him with the move of your choice.