Photo Finisher Achievement
Win a Multiplayer circuit race by less than 1 second
If you play public multiplayer races this may happen naturally, but it can be easily boosted with one other person in a private lobby. Note that you have to choose Circuit Race as the game type, and you can set this to one lap to make it faster. At that point it is a matter of both of you staying close together and crossing the finish line within one second of each other. The first place winner will get this achievement, so be sure to repeat it and let your partner earn the achievement also. It also can be earned in a private lobby against a single Drivatar. If you are following the guide for the multiplayer medals, you should get this without any deliberate effort.