Above the Law Achievement
Above the Law80
GTA Online: Reach Rank 100.
Every mission, activity and challenge you complete in GTA Online will net you Reputation Points (RP) which are essentially experience points that increase your overall Rank. In order to reach Rank 100, you will need to gain exactly 1,584,350 RP. It is recommended to complete as many Jobs and activities available whenever you are playing online in order to net a good amount of RP during your session. Also, do take note that playing with crew members and full lobbies will net your more RP at the end of an activity.
One of the best, fool-proof methods in ranking up quickly would be to a boosting partner and complete the "Criminal Records" Race. In order to load that up quickly, follow these steps: Pause > Online > Jobs > Host Job > Races > Criminal Records.
Now, just set the "Vehicle Type" to Super and "Laps" to TWO. On average, each lap will take about 35 seconds and you will gain around 500-2000RP at the end of the race, depending on when place you finish in. In addition to this, you will also net an additional 700-6000RP+ (dependent on your Rank) for various bonuses upon completing the very first lap of this race. The reason this race works so well when ranking up is because the race track is literally a full circle, so there is no worry for tight turns, collisions or traffic.
Overall, this achievement will require some dedicated hours of playtime, but with all the thrilling activities and unique missions around San Andreas, the road to Rank 100 shouldn't be too terrible. Of course, do take advantage of the Criminal Records method, as it will lessen the time it takes to reach Rank 100.
For further tips on how to effectively utilize this method, be sure to visit THIS THREAD. Thanks to Callum x360a, this thread compiles great information in grinding out RP at different Ranks in regards to the Criminal Records race on GTA Online.