Abate means ‘making something less intense’; ‘reduce or remove’.

Moderate: average in amount, intensity, quality, or degree.
Complement: a thing that contributes extra feature to something.
E.G. ‘Your necklace compliments your beautiful dress’, said Geeta to Shehar.
Decrease: ‘to lessen in quantity’.
Aggravate: ‘to intensify or make something more serious or intense’.
E.G. Politicizing the issue of riots will only aggravate the situation.

Hence, ‘aggravate’ is the best choice as the antonym of ‘abate’.