Here is the full list of all 12 Fireburst achievements worth 400 gamerscore.
Complete All Challenges For One Character.
Complete All Challenges For Three Characters.
Complete All Challenges For All Characters.
Get 100 Kills.
Kill Ten Opponents With Every Fireboost Type.
Kill Three Opponents In 5 Seconds.
Kill An Opponent In The Air.
Kill Ten Opponents In One Race.
Win A Race Without Getting Killed.
Win Five Online Races.
Win Ten Online Destruction Games.
Finish Fifty Online Games.