ruthlessness (n.)

• animality
• atrociousness
• barbarity
• barbarousness
• beastliness
• bestiality
• bloodiness
• bloodlust
• bloodthirstiness
• brutality
• cannibalism
• cruelness
• cruelty
• ferociousness
• ferocity
• fierceness
• hardness
• harshness
• heartlessness
• inclemency
• inexorableness
• inhumaneness
• inhumanity
• mercilessness
• pitilessness
• relentlessness
• sadism
• savagery
• truculence
• unfeelingness
• unmercifulness
• unyieldingness
• vandalism
• viciousness
• violence