My toughest corners for me are:
-Red Bull Ring: Castrol Edge (Turn 1)
-Fuji: Panasonic Corner (Turn 16)
-Apricot Hill: Happy Corner (Turn 11)
-Suzuka: Degner (turn before the tunnel)
-Laguna Seca: Corkscrew and turn after the tunnel before Corkscrew
-Spa-Francorchamps: Les Combes (7,8,9), Campus (14) and Chicane (Turn 19,20, Bus-Stop Chicane)
-Silverstone: Village and Arena (Turn 3 and 4)
-Brands Hatch: Sheene Corner (Turn 7)
-Trial Mountain: Turn 4
-Nürburgring GP: Castrol S (Turn 1) and Mercedes Arena
-Nürburgring Nordschleife: Adenauer Forst, Hatzenbach and Pflanzgarten