Tornados, or twisters, are among the world’s most terrifying weather events, tearing across land and often causing extensive damage and death. Defined as vertical funnels of frantically spinning air, they come from thunderstorms and can also hit land after gathering speed and forming spouts in bodies of water. And certain parts of the world are far more susceptible. From tornadoes with the highest death tolls to tragedies that could have been avoided, here are some of the deadliest and most devastating tornadoes of all time.