It was really a sinister move on his part.

Answer: Option C

Sinister : giving the impression that something harmful or evil is happening or will happen.
Malevolent : having or showing a wish to do evil to others.
Sinful : wicked and immoral; committing or characterized by the committing of sins.
Auspicious : conducive to success; favourable.
Right : morally good, justified, or acceptable.

Antonym of Sinister is Auspicious