Is the American Civil War is considered the worst Civil War in world history compared to other countries' civil wars?

The US Civil War is considered one of the Worst! Other terrible Civil Wars were the English Civil War and the Spanish Civil War.

Probably the worst Civil Wars were those in Cambodia, Rwanda, and Vietnam. The Vietnam War is often not considered with other civil wars because of the extensive involvement of outside parties. The Vietnam War consumed about 5 million dead, more than half of them being civilians.

The Cambodian Civil War and the aftermath of Cambodian Genocide saw the deaths of about 2.6 million people, around 20% of the entire population.

The Rwanda Civil War took about 800,000 lives, and also represented about 20% of the entire population.

By comparison, the US Civil War took about 600,000 lives from a population of about 31 million, or about 2%. That is very, very bad, but in many ways it does not compare with the horrors of the others listed here.