Here is the full list of all 60 DiRT 3 Complete Edition achievements. It takes around 50-60 hours to unlock all of the achievements on Windows.
Achieve a Platinum medal in all of the Gymkhana Academy tutorials
Use a flashback in the DiRT Tour after receiving terminal damage and then go on to win the race
Win a DiRT Tour race without using any driver assists
Complete a Time Trial race in a vehicle from each class of Rally
Win a race in every location
Win a DiRT Tour race in the Mini Cooper without receiving any damage
Win a Rally race in the DiRT Tour using the interior camera and the HUD switched off
Achieve a podium finish in the X Games Tournament
Achieve a podium finish in the Winter X Games Tournament
Win a DiRT Tour race in a Rally car from each decade
Reach Driver Rep Level 20
Reach Driver Rep Level 30
Achieve first place finishes and pass the DC Challenge in a World Tour event
Complete all Gymkhana Championships
Win the DC SuperSeries Championship
Achieve first place finishes in all DiRT Tour events
Score 500,000 Points in a Gymkhana Event
Beat the Bobsleigh in the Norway Speed Run DC Challenge
Smash every robot in a Smash Attack DC Challenge
Complete a clean run in a Gymkhana Sprint DC Challenge
Score 25,000 drift points in a Drift Showcase DC Challenge
Complete all of the DC Challenges
Achieve Silver medals in all of the DC Challenges
Achieve Gold medals in all of the DC Challenges
Achieve Platinum medals in all of the DC Challenges
Complete 25% of the Battersea Compound Missions
Complete 50% of the Battersea Compound Missions
Complete 75% of the Battersea Compound Missions
Complete 100% of the Battersea Compound Missions
Complete a Joyride online with at least 3 other players
Complete your first Pro Tour race on Steam
Win 10 Steam games (Pro Tour or Jam Session)
Complete 25 Steam games (Pro Tour or Jam Session)
Complete a Steam multiplayer race with a ‘Cautious’ rating
Complete a game of Invasion without any negative points (Pro Tour)
Remain uninfected in a round of Outbreak (Pro Tour or Jam Session)
Be the mouse in a Cat n Mouse game where your team has gone on to win the game (Jam Session)
Steal the flag from the opposing team 5 times in a game of Transporter (Pro Tour)
Win a game in each of the multiplayer party modes (Pro Tour or Jam Session)
Win a Steam race in Hardcore Mode
Earn enough fans to achieve the ‘Superstar’ title
Drive all of the cars from the Power and Glory Car Pack
Win a DIRT Tour event in a car from the Power and Glory Car Pack using a custom setup
Drive all of the cars from the Mud and Guts Car Pack
Complete a clean race with a car from the Mud and Guts Car Pack
Achieve first place in all DiRT Tour Monte Carlo Events
Drive in excess of 100 miles (161 km) in Monte Carlo
Win a Steam race in Monte Carlo (Jam Session)
Achieve first place in all DiRT Tour Shibuya Events
Complete a Time Trial in Shibuya
Win a Steam race in Shibuya (Jam Session)
Win DiRT Tour races using vehicles from each discipline
Complete 25 bonus Race Objectives
Achieve a podium finish in the Gymkhana Academy
Ace all trick types in a Gymkhana Championship event
Complete the tutorials in the Gymkhana Academy
Win a race in all weather conditions
Reach Driver Rep Level 10
Complete 5 bonus Race Objectives
Complete your first DiRT Tour race