She's 'rotten to the core'. [=she's a very bad person; she's a very dishonest person]
('Brit') He fancies you (something) 'rotten'. [=he likes you very much]
I feel 'rotten' [=I feel guilty; I am upset] about what I said.
(..) I say away. Go on, I'll follow thee - He waxes desperate with imagination - 'Tis not fit thus to obey him - To what issue will this come? - Something is rotten in the state of Denmark - Heaven will direct it - Nay, let's follow him Where wilt thou lead me? Speak, I'll go no further (..)2015 Hamlet