Comparatives, on the other hand, can be:
How much more beautiful was she than you?
How much younger are you than your brother?
N.B. The above restriction, concerning specifically the interrogative adverb phrase 'how much', applies even in cases where the simple adverb 'much' may be acceptable as a modifier. Thus, although we may not, in contemporary standard usage, have
*How much surprised were you?
(at best, an archaism)
we can still have, albeit in very formal usage,
I was much surprised to learn of his treachery.
(= more natural very surprised...)
Note, however, that the use of 'much' as a modifier of positive adjectives is essentially restricted to deverbal -ed forms.