The rapacious plunderers did not spare even the people living in the slums.

Answer: Option C

Warlike : disposed towards or threatening war; hostile.
Barbarous : extremely brutal.
Avaricious : having or showing an extreme greed for wealth or material gain.
Nomadic : living the life of a nomad; wandering.
Rapacious : aggressively greedy or grasping.

Synonym of Rapacious is Avaricious