Secondary Characters Along R.O.B.

[Phanton404]

Hello, having a secondary character can help getting through hard MUs to most people, so I'm very curious what others R.O.B. mains use for the matter.
What character do you guys think is the best choice here?
I use Sheik, since she helps me against Diddy, Mario and opposing Sheik. But, I'm not really sure if it's the best choice, some people would say Rosa, Cloud, etc.
I'm highly concerned on this matter, even though I use R.O.B. 95% of my matches.

 

[Crome]

Cloud is the universal pocket character, but he doesn't really do especially well vs. top tiers, just better than R.O.B. 8bitman (best R.O.B main) picked up Diddy recently and will start dual maining R.O.B/Diddy. I can't say much about this because I'm a pure solo R.O.B main.