Blur

To get this achievement you need to beat Shannon in her second one-on-one. First you need to unlock her races by getting 280 lights. Second you need to meet her career demands which are, Staying above 120 MPH for an entire lap, Land 15 reverse bolts, mine 20 cars, come first in all 6 events.

To land 15 reverse bolts put the mod on that gives you an extra bolt per bolt power up, get in front of a CPU and fire them backwards, you should get this after 1 or 2 races. To mine 20 cars you don't have to drop them behind you, you can forward hit other cars and it will count, you will get this by the time you finish all 6 races if you use mines regularily. Coming in first in all 6 events is easy to do, don't worry about fan runs or fan demands just finish in first, use the koenigsegg CCX-R. The last and hardest demand is for an enitre lap stay above 120 MPH. It does not matter where you start the lap as long as you are going 120 MPH for all the way around the track until you reach that same point again. I would suggest the 2nd event SanFran Sausalito - Bay Area Tour, and put the difficulty to easy. This track is quite easy to maintain 120 MPH while using the Koenigsegg CCX-R. The toughest corner is actually easy to take if you know how. At the start of the race grab a nitro and then a shield just before you enter the tunnels (incase a shunt comes for you.) The toughest corner is the S curve after the two splitting tunnels, make sure you start the curve by going to the far outside so you can go straight throught the S curve. If done right you will only drop to about 150 MPH and you can then just keep going normally. To make sure you didn't drop below 120 MPH you can use the nitro if you accidentally scraped the wall. The tracker will pop up on your screen when you've done an entire lap over 120 MPH.

Beating Shannon is actually very easy, put the mod on that gives your shunts extra power, there are plenty of shunts on Hollywood Hills. Collect 3 shunts and fire all 3 at her, usually she will destroy 1 (sometimes two) however you can usually make it to the next shunt before she gets to a repair because there is only 1 repair on the track. The first shunt is just at the start on the left, the second one is where the road splits its on the left, (you can also slow down to pick up the lightning bolt and use it right away its just after the shunt on the right) the 3rd one is after the long left hand curve on the inside of the straight. I would suggest waiting until the road splits into 3, fire 2 shunts and take the right path, pick up that shunt and fire it when you get back onto the road, then pick up the other shunt on the right hand side of the road and fire your last two. Also try to make her use all her power ups by driving closely behind her before you fire the shunts. Once she wrecks you win.

Shannon's one on one isn't that hard and is probably not why you're looking for help, like I did trying to get the 120mph for a full lap.

So this is a guide for that, the 120mph requirement.

The easiest place to do this is the second race, which features a wide road and only one place to screw up your 120mph speed.
I recommend setting it to easy, just so you won't be bothered as much. Use the first lap to make distance between you and everyone else and pull far ahead in first. During the second as you go through the sharp turn section you want to hit 120 as quickly as you can during or following the last turn, then in the 3rd lap try to grip the turn as far as you can until you are beyond where you hit 120 on your second.
(TO CLARIFY: Where the lap starts and ends can be anywhere, I used the place I typically crashed and lost my speed and for the 2nd actual lap tried to start this "120 lap" earlier than the spot I knew I could reach, I then finished my "120 lap" during my 3rd lap and despite crashing still completed it.)

hope that helped and didn't just confuse