Question

where should the coma(s) really be??

Sheldon Plankton dare I say it, may be the best badminton player I've ever seen.

Answer 1

Hey there! :D

Sheldon Plankton, dare I say it, may be the best badminton player I've ever seen. 

Since there is the independent phrase, 'dare I say it', you need to put commas before and after it. Sheldon Plankton is a separate fragment of the sentence. 

I hope this helps!
~kaikers

Answer 2

This is just one coma off. 

Sheldon Plankton, dare I say it, may be the best badminton player I've ever seen.