Use the Cheat Code menu (Options → Cheats): Enter iammostwanted → unlocks Challenge Series 34 (Burger King Challenge) only. That's the only official code.
Save editing (PC): Tools like NFS MW Save Editor can flag Blacklist defeated, but corrupts save if done wrong
Blacklist Order (Cars Unlocked)
Razor (BMW M3 GTR) – final
Ron (Aston Martin DB9)
JV (Dodge Viper SRT-10)
Webster (Corvette C6)
... down to Sonny (VW Golf GTI)
Play the pursuit loop—it's the best part of the game.