In December 1851, two waterspouts moved onshore at the western end of Sicily, becoming large, violent tornadoes. This was as a pair of tornadoes, but details are very scarce; it may have been a single multiple-vortex tornado. It remains the second deadliest tornado event in recorded European history.
http://www.grayflannelsuit.net/blog/the-10-deadliest-tornadoes-in-world-history
2011’s deadly tornado in Joplin, Missouri — just one of many to strike the American Midwest that weekend — is a stark reminder of that fact. In total, more than 1,000 tornadoes touched down in the U.S. in April 2011 — the most active month on record.
http://www.grayflannelsuit.net/blog/the-10-deadliest-tornadoes-in-world-history
What at one time was thought to be the record holder for the longest tornado path is now thought to be the longest tornado family, with a track of at least 293 miles (472 km) on May 26, 1917 from the Missouri border across Illinois into Indiana.
https://en.wikipedia.org/wiki/Tornado_records
Matt Pearce. A tornado that swept through Oklahoma on Friday was the widest tornado in American history, the National Weather Service said Tuesday. The El Reno, Okla., tornado scraped out a damage path up to 2.6 miles wide and 16.2 miles long, a swath at points wider and longer than Manhattan.
http://www.latimes.com/nation/nationnow/la-na-nn-el-reno-tornado-20130604-story.html
It is considered an F5, though tornadoes were not ranked on any scale in that era. It holds records for longest path length at 219 mi (352 km), longest duration at about 3.5 hours, and fastest forward speed for a significant tornado at 73 mph (117 km/h) anywhere on Earth.
https://en.wikipedia.org/wiki/Tornado_records
This article lists various tornado records. The most extreme tornado in recorded history was the Tri-State Tornado, which roared through parts of Missouri, Illinois, and Indiana on March 18, 1925.
https://en.wikipedia.org/wiki/Tornado_records
The deadliest tornado in world history was the Daulatpur–Saturia tornado in Bangladesh on April 26, 1989, which killed approximately 1,300 people.
https://en.wikipedia.org/wiki/Tornado_records
But while the U.S. is home to the most tornadoes on a yearly basis, advances in research and early detection have helped reduce the number of fatalities from twisters. As a result, the list of the 20 deadliest tornadoes (or tornado outbreaks) ever contains just five from the United States. Here are the full top ten.
http://www.grayflannelsuit.net/blog/the-10-deadliest-tornadoes-in-world-history
The National Weather Service says the deadly tornado that struck near Oklahoma City late last week was another top-of-the-scale EF5 that packed winds reaching 295 mph. The weather service also says the twister's 2.6-mile width is the widest ever recorded. In this May 31, 2013 file photo a tornado forms near Banner Road and Praire Circle in El Reno, Okla.
http://www.latimes.com/nation/nationnow/la-na-nn-el-reno-tornado-20130604-story.html
In raw numbers, the Joplin tornado of May 22, 2011 is considered the costliest tornado in recent history, with damage totals near $2.8 billion (2011 USD). Until 2011, the  Bridge Creek-Moore tornado  of May 3, 1999 was the most damaging.
https://en.wikipedia.org/wiki/Tornado_records
what is the biggest tornado in history
Violent tornadoes are the biggest tornadoes in history.