MX vs. ATV Reflex

To get this achievement, you have to win 3 Snake mini game rounds in a match. When choosing what multiplayer type you want to play, choose mini games. You will be transported into the waiting track (same place as a single player race), and depending on what the billboard displays is the next mini game you'll play. It's either going to be Snake or Tag. Just keep playing until Snake comes up.

Once a Snake game starts, make sure to win 3 times if I remember correctly. The rounds will keep going until someone reaches 3 wins. So say you win 2 in a row, then another person wins the next, and you win the 4th round, the match will then end and you will ultimately win and unlock the achievement.

A tip that really helped me to win a lot is that at the start, go straight towards the barrier. Once you reach the barrier and are within a few feet of it, turn left of right depending on your opponents, you want to go opposite of what side they're on. Now simply make huge circles on your half of the course, riding next to your colored line you make. Soon enough your opponent(s) will mess up and run into your line. Win 2 more times and achievement unlocked!

Note: You will lose by crashing, running into any of your opponents colored lines, or running into your own line. So make sure to be careful!