Here is the full list of all 44 London 2012: The Official Video Game achievements worth 1,000 gamerscore.
Hit every target at Station 4 in Skeet
Wore an alternative national kit in an event
Qualified for the finals of every event in an Olympic Games mode campaign
Perform 10 Power Shots in a Table Tennis match
You have won a total of 5 Gold medals in Quick Matches or Custom Matches
Won an Xbox LIVE Tournament
Played an Xbox LIVE Tournament with one or more friends
Every player in a Challenge Event scored more than their share of the team's 3-Star target score
Performed 30 foul attempts in field events over your career
Earned a Gold medal in every Jumping event, while representing a nation
Won a Table Tennis or Beach Volleyball match without losing a point
Performed 10 ace serves over your career
Received a perfect ten from one of the judges in a Diving event
Earned a Gold medal in every Versus event, while representing a nation
Earned a Gold medal in every Shooting event, while representing a nation
Scored ten or more on every target in a round of Rapid Fire Pistol, while representing a nation
Earned a Gold medal in each of the 5 types of Swimming event
Earned a Gold medal in every Gymnastics event, while representing a nation
Earned a Gold medal in every Throwing event, while representing a nation
Broke a World Record
Earned a Gold medal in each of the 4 types of Track events
Touched the last hurdle and still won a medal in 110m Hurdles
Won a Race by 0.07 seconds or less
Earned 3 Gold medals in team events
Beat your personal best in Team Archery or Synchronised Diving
Created and played through a custom playlist
Completed the Men's K1 Kayak Single course with no penalties at all, while representing a nation
Touched the bar in a High Jump and still cleared it successfully
Competed in a Quick Match or Custom Match for National Pride
Completed a multiplayer game, while representing a nation
Emoted first out of a group of players while being introduced for a race event
Earned a Gold medal in The Olympic Games mode
Qualified for the finals of an event in The Olympic Games mode
Used a Retry Token, and got a better result in the top 3 places
Win an Events Mode session with four players competing
Unlock all available sporting accessories
Earn 20 medals in a single Olympic Games Campaign
Earn the Gold medal in every event of a medium or hard Olympic Games mode campaign
Beat your own personal best in every event possible, irrespective of gender.
Hit the bullseye camera of the archery target, while representing a nation
Distance run over career is 42.195km
Complete a Challenge Set with 4 players
Earn 9 Challenge Stars in a single Challenge Set
Complete all Challenge Sets for any controller type