The ’81 Ferrari 126C gets my vote, and I think that this quote from Harvey Postlethwaite sums up just why the car won the races against all odds…
“That car…had literally one quarter of the downforce that, say Williams or Brabham had. It had a power advantage over the Cosworths for sure, but it also had massive throttle lag at that time. In terms of sheer ability I think Gilles was on a different plane to the other drivers. To win those races, the 1981 GPs at Monaco and Jarama — on tight circuits — was quite out of this world. I know how bad that car was.”
and in keeping the colour, Im adding the Ferrari 246 of 1960 and 1959. Controversial, but for 1960 the car one only 1 race and that was the Italian GP which was boycotted by the British teams such as Cooper, B.R.M and Lotuses of TL and Rob Walker. More so, assuming Wikipedia is even correct, the organisers helped the Fezza’s by making use of the banking to maximise the cars excellent top-end speed!
The previous year it won 2 races, and more to that has to be because it had (the criminally under-rated) Tony Brooks piloting the car, and again, on tracks which made best use of its 1 advantage over the Mid-Engined cars, Its top speed at the French GP at Rheims and the German GP at AVUS