Here is the full list of all 40 Assetto Corsa Competizione achievements worth 1,000 gamerscore.
Go 150km/h
Go 280km/h
Travel 1000km in total
Drive for two hours in a session
Drive more than 100km in one session
Stay in an opponent's slipstream for 5 seconds
Complete 5 clean laps in a row (do not cut, lose control, or go too slow)
Complete 10 clean laps in a row (do not cut, lose control, or go too slow)
Complete a Championship
Complete the Career mode
Complete 10 laps in Practice mode with all driving assists turned off
Complete 10 valid laps in Hotlap mode
Try every car and every track
Win a race with every car
Take part in a night race
Take part in a multiplayer race
Lap every opponent at least once within a single race (minimum 15 opponents)
Earn a track medal (on any track)
Win a race from the back of the grid (minimum 10 cars)
Stay in first place for the entire race (minimum 10 cars)
Drive your first lap at Spa
Complete a lap at Spa in under 2:25
Get on a special event leaderboard
Complete a race without damages (Valid hotlap speeds, 10 cars minimum, not disqualified)
Receive your first penalty
Start in pole position in any race (Earned from a qualifying session)
Totally destroy your car
Break your cars engine
Get pole, fastest lap, and race win in the same race (Pole from qualifying and 15 opponents minimum)
Complete a Short Career achieving a gold cup
Complete a Medium Career achieving a gold cup
Complete a Long Career achieving a gold cup
Win a Championship
Earn all medals for a track (any single track)
Earn all track medals for all tracks
Achieve Bronze driver category
Achieve Silver driver category
Achieve Gold driver category
Achieve Platinum driver category
Achieve a session Consistency Rating of 99 (NB: very difficult to acquire)