For this achievement, you have to defeat Toru Sato AKA: "Bull", who is number 2 on the Blacklist.
The requirements to face him are:
(8) Race Wins
(5) Milestone Events
His ride is Mercedes-Benz SLR McLaren and he is harder than other racers to beat, he mainly uses his speed on straights to overtake you, just make sure you match him and you'll beat him easy, handle well on corners thats the key, he ain't very good on corners, except in his sprint races, he can go quite fast and can be quite hard to beat in them but the circuit race should be simple, I beat him quite easy in this.