The correct option is D civilised
The word 'barbarians' refers to an uncultured or brutish person.
Option A, bad refers to something of a poor quality or low standard.
Option B, uncivilised refers to not being socially, culturally or morally advanced.
Option C, cruel refers to wilfully causing pain or suffering to others.
Option D, civilised refers to being polite and well mannered.
Thus, according to the meaning, the word 'civilised' is the opposite of the word 'barbarians'.