This hyper-tuned Cadillac has been revealed as the worldâs fastest family car with the frightening vehicle capable of a staggering 242mph. See SWNS story SWFAST; The incredible CTS-V will outsprint any Lamborghini, Ferrari or Porsche ever built with only a handful of supercars quicker. It is the work of Texan tuner John Hennessey – who saw claims made by the boss of Bugatty as a challenge. Wolfgang Durheimer recently said its forthcoming Galibier model will be the fastest four-seater in the world, capable of more than 235mph.