12 worst presidents of the USA

The latter half of the Phoenix Program of mass torture.
Overthrow of the Chilean government.
Chemical warfare by Agent Orange and napalm in the US-Vietnam War.
Ignored Bengali genocide.
Kurdish rebels killed by Nixon’s betrayal.
Mass deaths in Operation Condor.
Mass deaths by ideological blindness in the US-Vietnam War.
Pardoning mass murderer Lt. Calley.

Second Worst: Ronald Reagan
Mass deaths by collaborating with genocide in Guatemala, US sponsored terrorism in Nicaragua, supporting repression in El Salvador and Honduras, US bombing El Salvador, and invasion of Grenada.
Chemical warfare, Plan Colombia spraying of herbicide glyphosate.
Selling biological weapons material to Saddam Hussein.

Third Worst: Andrew Jackson
Genocide against the Five Tribes. Slave trader.

Fourth Worst: James Buchanan
Ignored California Indian genocide. Incompetence worsening the Civil War.

Fifth Worst: James Polk
Making California Indian genocide possible. Provoking the US-Mexico War. Expanded slavery and partly contributed to eventual Civil War. Slave trader.
Sixth Worst: Millard Fillmore

Ignored California Indian genocide. Being a presidential candidate for Know Nothing terrorism.

Seventh Worst: Bill Clinton
Ignored Rwandan genocide. Even Clinton admits 300,000 could have been saved.
Incompetence in Somalia invasion and Branch Davidian standoff.

Eighth Worst: Gerald Ford
Ignored in genocide in East Timor.
Continuing Operation Condor begun by Nixon.

Ninth Worst: Harry Truman
Atomic warfare targeting Japanese civilians.
Chemical warfare by napalm in the Korean War.
Targeting civilians during World War II.
Atomic bomb testing on Pacific Islanders.
Many argue Truman largely started the Cold War. His responsibility is shared with many.

Tenth Worst: William McKinley
War of aggression against Filipinos, failure to stop atrocities.
Seizure of Guam, Hawaii, Puerto Rico, and Samoa.

Eleventh Worst: George W Bush
Deaths by torture.
Chemical warfare, herbicide in Plan Colombia.
Mass deaths by incompetence and ideological blindness in the Afghanistan and Iraq Wars.
Mass deaths in Hurricane Katrina, mostly preventable.
Blocking chemical warfare treaty and nuclear free zone in the Mideast.