The Koenigsegg Agera is one stupendously quick supercar . It can travel from a dead stop to 186 miles per hour and back down to zero in a scant 21.19 seconds. That's not even enough time to sit through a car insurance commercial.The Porsche 911 GT3 RS 4.0 isn't quite as quick, but it can boast some serious performance chops all its own. The race-ready 911 can hit 62 miles per hour in just 3.6 seconds, and a trip to 120 miles per hour takes only 11.5 seconds.But while the GT3 RS 4.0 can't quite keep up with the Agera once the rubber starts rolling, this athletic Porsche can stop a bit more quickly. The GT3 RS 4.0 has reportedly beaten the Agera's braking record of 186 mph to zero in 6.66 seconds , and we have the video that proves it. Hit the jump to watch the speedometer plunge from 186 mph to zero in only 6.5 seconds.