In what would become the United States, the Salem Trials were the most deadly over a short period of time. The same number were killed in 9 months that were killed in colonial America in the 50 years preceding the Trials; when you then look at accusations that didn't go to trial (upwards of 150 during the same 9 month period) Salem becomes a perfect example of a society in complete social collapse.

As far as bloodiest, Salem is nowhere close. The European witch hunts claimed the lives of tens of thousands of people, with a large majority living in what is today Germany and France. Gutenberg's movable type, popularized in the 1440s, saw an explosion of popular literature on witchcraft, demons, and Satan's influence on everyday life brought to the public in a readable manner - and the Vatican encouraged early inquisitions into charges of witchcraft.

As crops continued to fail, the Holy Roman Empire sought to reestablish dominance, and religious tension brought on by the Reformation increased; accusations brought on hysteria which brought on more accusations. In some of the most notable cases, such as Wuerzberg and Trier this resulted in hundreds of people being executed int he span of a few years. These executions varied, some ending in torture, other in hangings, and others still beheadings or burnings. (The idea of witches being burned at the stake comes from its usage in the German and Swiss executions).

Cornell maintains an online database on Witchcraft that is worth looking at if you're interested in the topic.