Storm-chasers Basehunters Chasing used a time-lapse camera to capture this footage of a supercell thunderstorm forming over the plains of Wyoming on Sunday. And HOLY SHIT. Supercells are terrifying. From Wikipedia:
While tornadoes are perhaps the most dramatic of these severe events, all are dangerous. High winds caused by powerful outflow can reach over 148 km/h (92 mph and downbursts can cause tornado-like damage. Flooding is the leading cause of death associated with severe weather.
Note that none of these severe events are exclusive to supercells, although these events are highly predictable once a supercell has formed.
[H/T: Viral Viral Videos]