Remove an item from a list contained in another item in python

[supuflounder]

I have this randomly generated list in python:

l = [[2,3,4,5],[2,3],[7,8],[2],[4,5,6]]

and i want to remove the items [2,3] and [2] because they are completely contained in the first item [2,3,4,5].

newl = [[2,3,4,5],[7,8],[4,5,6]]

How do I do that?

What about [4,3], [2,5], [6,4]. [4,2,5]?

It is looking like O(n^2); it may be worse. Knowing the actual rejection criteria is important, because that determines the complexity. It is not possible to infer the desired result from the examples given.