Is clouds looked dark a complete subject

I would say it is not a complete subject or thought for that matter because a complete thought would include a subject which in this case is considered the clouds and a predicate which is a verb looked and a complete thought to finish that off. So Clouds looked dark is not an entirely finished though it has more to go.

To be honest, I'm not entirely sure if it would be considered a complete sentence or not. Technically speaking it has a subject and a verb, but I don't know if it has a complete thought. I think it should read: The clouds looked dark.