I think mt Viper ACR is one of my most powerful, BHP isn't the vital number, it's torque that's needed, and it has I think 142kgfm of the stuff, now that eats tires.
BHP wise, either my Escudo or Speed 12 (not at my PS3 currently to check), although a notable car would be the Dodge Neon, over 600bhp in an FF car, pretty insane.