Too bad the Audi Quattro gets way too much credit. Hell it was even beaten in a championship by the unknown and forgotten rear wheel drive Lancia 037, the last two wheel drive car to win a WRC.
The Delta S4 is the embodiment of the Group B era, it was by far the craziest, fastest and most mental car out there. A mid-engined turbo and supercharged car with more then a 1000hp and weighing just 890kg is just too much too handle.
Toivonen himself was complaining about the car being too powerful for a rally like the Tour de Corse. He found it very hard to keep the car balanced on the road and admitted it was very exhausting.