I can't say how to defeat Meta Knight with Ness. IC's on the other hand can be dealt with, I believe. Things you want to focus on when fighting the Ice Climbers are avoiding their grabs which are probably the worst in the game, and separating the two.
Advantages
Disadvantages
The last two advantages aren't really advantages, I guess. But it is true that you can gimp Nana, even Popo, when they're off the stage. Without his ally, Popo has a harder time returning to the stage safely. Just avoid the Ice Shots as they return and give them a problem. Also, if they're above you, use your PK Thunder well and try to juggle one or the other. Popo is a bigger threat than Nana, but again, you want to separate the two. One more thing, take them to a stage with platforms. It shouldn't be hard to find a stage with platforms.
Advantages
- PK Fire blocks off Ice Shots
- PK Fire has decent ground range which should keep you out of harms way
- PK Fire can trap IC's for a bit, but is a lot more useful when they're desynced, causing them to worry about their ally for a bit
- PK Fire is also good when they're using their Blizzard
- Forward air has good range, use it
- Neutral air is good for separating the IC's
- When Nana is off the stage, you can spike or nair her
- One Ice Climber is easier than two
Disadvantages
- Their infinite for one
- Ice Shots go far
- Ice Shots have a possibility of gimping
- Blizzard has a possibility of gimping if used correctly
- Unable to get grabbed without being punished
- Better at baiting
The last two advantages aren't really advantages, I guess. But it is true that you can gimp Nana, even Popo, when they're off the stage. Without his ally, Popo has a harder time returning to the stage safely. Just avoid the Ice Shots as they return and give them a problem. Also, if they're above you, use your PK Thunder well and try to juggle one or the other. Popo is a bigger threat than Nana, but again, you want to separate the two. One more thing, take them to a stage with platforms. It shouldn't be hard to find a stage with platforms.