Here is the full list of all 45 FlatOut 4: Total Insanity achievements worth 1,000 gamerscore.
Purchased all cars of the game
Completed Career Mode
Scored over a 100,000 in a race
Completed FlatOut Mode with all gold
Completed FlatOut Mode
Upgraded an AllStar car at the maximum
Bought at least 2 cars in each class, Derby, Classic and Allstar
Won a race in Derby, Classic, AllStar classes
Earned 123456 cash in Career Mode
Killed Three opponents in the same race (offline)
Completed all stunts with gold in FlatOut Mode
Drove a total distance of 500 miles
Completed all stunts with bronze in FlatOut Mode
Made the perfect score in a stunt game
Destroyed 50 opponents (offline)
Beaten a Time Trial with gold in Career Mode
Finished consecutively 10 times on podium in Career Mode
Won a race with the maximum car parts on your car
Got all available skins for a Derby car
Ejected your driver 100 times
Upgraded a car once
Hit 3 cars with the same activated weapon in Assault Mode
Completed your First Cup in Career Mode
Destroyed your first opponent (offline)
Won 25 online races
Won 20 races in Assault Mode online
Destroyed 2000 breakables
Won 10 online races
Won 5 races in Assault Mode online
Won a race in Assault Mode
Had the 4 different weapons used in Assault Mode
Won a race without crashing (100% Full HP)
Jumped at least 100m long with your car
Slammed 100 opponents in online races
Won an online race
Won 15 races in Arena Mode
Destroyed 20 Opponents Online
Been both Survivor and Eliminator at the same time in 5 Arena Deathmatches
Completed your first race in Arena Mode
Wrecked 5 vehicles during a round in Arena Mode
Recovered the flag 10 times in the Keep the Flag Mode
Destroyed your car for the first time
Burnt nitro continuously for at least 5 seconds in a race
Emptied all your nitro for the first time from full to empty
Kept the flag for 66 seconds in Keep the Flag Game Mode