I just wanted to add on my experience as I had some problems with getting this achievement and how I quickly figured out a way to make wins consistent.
So, I used TA's walkthrough regarding this achievement, but I was getting inconsistent results using Skip to End of Session in the pause menu after the light turns green, because you can't screw up the launch. The skip to end of session option won't automatically give you the win. It takes into account current position and the state of your vehicle, etc. So if you get a bad launch and the AI gets ahead of you, then the skip session isn't going to catch you up every time. It's the equivalent of two computers racing each other, but you're just fast forwarding to the end.
But first, what I recommend, is to go to the race options, change it to one opponent, 2 laps, AI difficulty to 1, and set it to where the player starts in the pole position. I had better results with two laps because it gives your vehicle time to distance itself once the game has finished simulating the race.
Now for the solution. What we want to do is give our vehicles the best start possible so the game can simulate the race with our vehicles in the lead from the get-go. Just skip the cinematic and hit pause when the camera sets itself behind the vehicle. You'll notice that the Skip to End of Session option is locked. It won't unlock until the light turns green. So, instead, select Simulate Remainder of Session. This turns our vehicles into AI drivers for the entire race, which is important because the AI is pretty consistent on the launch and we get the lead because of the pole position option we set.
So, after you select Simulate, you should see that the Skip to End of Session option unlocks even though the light hasn't turned green yet. Now, you can select it to skip to the end. For me, it made getting wins more consistent, but I did have the occasional loss, maybe 1 out of 10. If you feel you are getting more than a couple random losses with this method, what you can do is Simulate, then exit the menu, let the vehicles launch, and wait about 5-7 seconds for the AI to distance itself from the opponent, then Skip.
Sorry for the long post, but if something isn't clear, just let me know in the comments and I'll try to tidy it up.