World War I was started by the assassination of the Austria-Hungarian Archduke Francis Ferdinand. To quote my history textbook:
Waiting for him [Ferdinand] along the designated route were seven assassins armed with bombs and revolvers. The first would-be assassin did nothing, but the next man in line had more resolve and threw a bomb into the open car. … Trying to kill himself, the bomb thrower swallowed cyanide and jumped into a nearby river. The old poison only made him vomit, and the water was too shallow for drowning.
That must be the most epic fail of an assassination attempt in history. Not only did the bomb glance off Ferdinand’s arm without hurting him, he tried two different methods to commit suicide and neither worked.
In the meantime, Princip swallowed poison, which also only made him sick. When he tried to turn the gun on himself, a crowd intervened.
Princip, another of the assassins, shot Ferdinand and his wife dead, then managed to fail at committing suice as well. While ultimately causing a war that lead to millions of deaths, the assassins were not very good at assassination.
(Traditions & Encounters, Bentley and Ziegler, McGraw Hill, page 763)