The badges for the achievement are:
Finish 10 events in Diamond Bracket
Finish 10 events in Platinum Bracket
Finish 10 events in Gold Bracket
Finish 10 events in Silver Bracket
Compete in 50 Race Events
Compete in 50 Trick Events
Compete in 50 Survive Events
Compete in 50 Custom Events
Compete in an event with 50,000+ players
Join an event with a 1,000,000 credit drop (Must be done after getting badges for 10,000 and 100,000)
Earn 1,000,000 credits through Global Events overall
For Diamond Bracket wins simply create a custom event that is 10 minutes long, race/trick/survive in it, then you will get diamond. The progress for the badge doesnt count until the event is over and you have dashboarded and came back into the game.
As for Platinum-Silver Brackets you need to earn these legitimately through Global Events already in place. You can just join events and do your best and see what you get. The more people there are, the less that times/points will be spread apart from each bracket. My advice is to do survive events that are close to ending and die right after you earn the badge you want. For example: If Bronze is at 100m and silver is at 200m, get to 201m and die to earn silver. (Assuming nobody joins after that)
For competing in Race/Trick/Survive/Custom events I suggest playing a lot of events for your Bracket Badges. You can, though, boost these by creating custom events that are only 10 minutes long. The progress will count as soon as you create the event. There is no need to start it up, or even choose a character. Just go to Custom Event and create a Race or Trick and as soon as you see the character selection screen it will have counted so you can just back out. Survives can be created but only on tracks that have a survive event at all. You can have 3 custom events up and running at a time, which is why you make each one 10 minutes, so you dont have to wait too long.
For competing in an event with 50,000+ players, I regret to inform you that if you don't have it already then you probably can not get it. In the first week of launch there was an event that was a week long that managed to accumlate only 58,000 or so players before the event ended. Since this event is no longer running (and there appears to be no event like it that could accumulate that many people) it would appear that you can't get this badge if you don't have it. There is talk of getting the badge lowered/redone (considering on the PS3 the event never made it 50,000 before it ended) so I will keep this updated if that is the case.
For joining an event with a 1,000,000 credit drop you need to join the event AFTER you already have the badges for joining an event with 10,000 and the badge for 100,000. Basically what im saying is you need to get them in order otherwise you will waste the million credits. As of right now there is an event in the Himalayas that has a 1,000,000 credit drop Survive Event. It seems to be reaccuring and has a week long time limit.
For earning 1,000,000 credits in Global Events accumulatively you will probably get this over time. The higher the drop cost is, the more money you receive if you do well. If you really don't have this by the time you join the 1,000,000 credit drop event then doing even slightly well will earn you over 1,000,000, but i'm sure you will have it long before then.
Update: Joining any Global Event will get you the 50,000+ players since EA has unlocked this badge!