This achievement requires you to,
Complete 1 challenge pack to 100%
Complete 3 challenge packs to 50%
Complete the ultimate comback challenge
Complete the retribution challenge
First for completing 1 challenge pack to 100% i would recommend doing Drivers Ed, this is the first one you unlock and also the easiest, it only requires you to get accumulative objectives which you can check in your challenge menu from multiplayer, you will get these while you are going for rank 50, if you don't plan on going to rank 50 you could boost these but its not worth it.
For completing 3 challenge packs to 50% i recommend doing the Drivers Ed, Demolition and Daily, Demolition will take longer to complete than Drivers Ed, first of all because you have to be a high enough rank, and because it takes a little bit more skill. By the time you complete Drivers Ed you will have demolition unlocked and you can start working on that, remember you only need 50% of it done. The last easiest one is the Daily challenges (you should have this unlocked after you finish 50% of the demolition challenges or earlier), this is easily done to 50% because one of the challenges requires you to complete 20 races and by the time you do that you will have at least 7 of the other challenges done (which gets you 50%). If you don't keep playing until you do because they are quite simple to get (they reset everyday at midnight so you can keep getting fans off of them every day which is good for getting to level 50.)
Now on to the specific challenges, the retribution challenge is located in Demolition, it requires you to get 5 revenge attacks during a single ranked event (any event will do). The easiest method to do this is go into a motor mash and play it. You get a revenge attack almost everytime you hit someone, but if you don't know how to get one you first need to be hit by another player then you need to hit them back.
The final challenge and by far the hardest and longest is ultimate comback. This challenge is under the Ace challenges (which you don't unlock until level 30), you may or may not have this unlocked by the time your done all the other challenges, if you don't then you will just have to wait until you reach that level. If you do then to get this challenge it requires you to go from first place (You cannot start the race in first) to last place and then go on to win the race. This does not have to be on the last lap or anything, as long as you are in first at anytime and last at anytime and win you will get this. The easiest method is to get a small group of people together in your party and join a gametype with not many people (hardcore, community, or world tour are usually empty) and just boost it. If you play all the way to 50 however, you can get this by starting a race in first place then picking up a nitro or two and wait until you are in last (the less amount of people the easier) then when you are in last nitro back to first (best done near the start if possible and on a long race, A class races are usually 3-4 laps which gives you plenty of time) once you finish in first the challenge will unlock.
Remember the daily challenges reset everyday so make sure to have the daily challenges done on that day.