Humanity at its Worst is not a handbook for prevention but rather a research driven summary of one of the most disturbing features of the 20th and 21st centuries. Its intent is to provide a basis for understanding of these incomprehensible crimes against humanity. The catalogue is large, disturbing, and troublesome. It is dedicated entirely to assisting readers understand the circumstances of people across the world who must contend with these extreme inhuman actions. Each chapter examines numerous factors including the conditions of the victims, the number of such incidents, the loss of lives, the conditions of women, and children past records of major incidents of this kind. The accounts of genocides examine the differing interpretations of genocide from legal viewpoints, as well as analysing the influence of race, ethnicity, nationalism, and gender. The book is divided into three main sections: Part One clarifies fundamental terms such genocide, war crimes, ethnic cleansing, mass murder, crimes of aggression, international criminal law, the Rome Statute of the International Criminal Court, The Foundation of Genocide Convention, and lessons from 20th century genocide. Part Two examines the 20th century genocides; Nazi Holocaust; Armenian Holocaust; Holodomor Ukraine; Cambodia, Congo, Sudan, Ruwanda, Burundi; Ruwandan Genocide; Yugoslavia; Kurdish, the 21st century genocides, Darfur; Iraq; 2006 Lebanon war; Baluchistan; 2009 Sri Lanka; Civil war in Syria 2011 to today; Rohingya; Yazidis ethnic and religious cleansing; Christian prosecutions; Boko Haram; Congo; ISIS war crimes; Yemen; Libya civil war. Part Three tackles Terrorism, Failed States, and UN Action to end violations of Human Rights.