Need for Speed Payback

To earn this achievement, you need to complete 5 events in an online speedlist.

The speedlists in NFS are similar to the ones in Forza Horizon. To access the speedlists simply pause the game and navigate to the multiplayer tab. Once the game is done loading you can select a casual, ranked, or private speedlist. Unless you plan on playing multiplayer past achievements in this game, it's better that you select ranked speedlist because you need to complete in 10 events in a ranked speedlist for another achievement.

Each speedlist consists of 5 races, and they are either offroad circuits/sprints or race circuits/sprints. Before you join a speedlist you can select the cars you want to use in the speedlist at the bottom of the screen. Once you're ready select the ranked speedlist and the game will either throw you into an ongoing speedlist or a new one. Once you're in, simply race through the events.

Once the speedlist has finished and the final points tally is complete, you'll get the achievement regardless of whether you raced in all 5 races. Don't forget winning isn't important. Most people have lv 399 cars in ranked multiplayer so if they leave you in the dust don't worry as you'll still get the achievement no matter what place you finish.

According to comments, you now have to race in a full speedlist from start to finish, so you can no longer join in, compete in less than 5 events, and get the achievement. If you join in late, just stick around until the next one starts to ensure you're there for all 5 events.