No, it's an antonym.
purer and purest
More complex is the comparative form, used to compare two things. Worst, and most informative are the superlative form. Well is a simple adverb.
simplest
the simplest
simpler, simplest
simpler
simpler, simplest
They are "simpler" and "simplest".
simpler, simplest
beautiful - uglyold - newhot - cold
There is no such thing as a simple complex carbohydrate. Carbohydrates are either simple or complex; they cannot be both.
The comparative of plain is 'plainer' and the superlative is 'plainest'.