Dubbing animations and movies is much harder than dubbing documentaries.
Is it necessary to repeat dubbing here?
English Language Learners Stack Exchange is a question and answer site for speakers of other languages learning English. It only takes a minute to sign up.Sign up to join this community
If you don't care for the repetition, try
Animations and movies are much harder than documentaries to dub.
Animations and movies are much harder to dub than documentaries.
or (if you're very fussy)
Animations and movies are much harder to dub than documentaries are.
As TRomano pointed out, "more harder" is ungrammatical (though frequently seen, sometimes as humor).
Repeating "dubbing" is important, in the form of the sentence you give, because it's not completely clear without re-reading that it's dubbing documentaries that's hard. TRomano's rephrasing would be a good way to avoid repeating "dubbing" if that's what you want to do.