The correct option is C ethical
The word 'unscrupulous' refers to having o showing no moral principles.
Option A, superfluous refers to something unnecessary, especially through being more than enough.
Option B, single minded refers to concentrating on only one aim.
Option C, dedicated refers to being dedicated to a task or purpose.
Option D, ethical refers to being morally good or correct.
Thus, according to the meaning, the word 'ethical' is the opposite of the word 'unscrupulous'.