There are a few different ways to answer this question, depending on how you define biggest." If you're looking at the assassination that had the most far-reaching effects, then it's probably the assassination of Archduke Franz Ferdinand in 1914. This event sparked the start of World War I, which ultimately led to the deaths of millions of people.If you're looking at the assassination that claimed the most lives, then it's probably the assassination of President Abraham Lincoln in 1865. Lincoln was shot by John Wilkes Booth while attending a play at Ford's Theatre, and died the following morning. Booth's plan was to also kill Vice President Andrew Johnson and Secretary of State William Seward, but those attempts failed.There have been many other notable assassinations throughout history, including those of JFK, MLK, and Gandhi."