【Intensify】 , 【aggravate】 ,  【heighten】 ,  【enhance】  mean to increase markedly in degree or measure.

【Intensify】 implies a deepening or strengthening of a thing or especially of its characteristic quality.

【Aggravate】 implies a manifest increase in the seriousness of a situation or condition that is already unpleasant or difficult.

【Heighten】  and  【enhance】  both imply a lifting or raising;  【heighten】 , however, tends to imply a lifting above the ordinary, the trite, or the commonplace, and a consequent increase in sharpness and poignancy, and  【enhance】 a lifting above the norm or the average in desirability or attractiveness by the addition of something that increases the value, charm, or prestige of the thing enhanced.