Here is the full list of all 44 London 2012: The Official Video Game of the Olympic Games achievements.
Earn 3 Gold medals in team events
Beat your personal best in Team Archery or Synchronised Diving
Beat your own personal best in every event possible, irrespective of gender
Earn a Gold medal in every Gymnastics event, while representing a nation
Win a Table Tennis or Beach Volleyball match without losing a point
Play an Online Tournament with one or more friends
Complete all Challenge Sets for any controller type
Complete a Challenge Event, where every player scores more than their share of the 3-star target score
Complete the Kayak Slalom K1 course with no penalties at all, while representing a nation
Win a Race by 0.07 seconds or less
Win a total of 5 Gold medals in Online Quick Matches or Online Custom Matches
Earn a Gold medal in every Jumping event, while representing a nation
Distance run over career is 42.195km
Perform 30 foul attempts in field events, over your career
Hit the bullseye camera of the archery target, while representing a nation
Perform 10 ace serves over your career
Earn a Gold medal in every Versus event, while representing a nation
Hit every target at Station 4 in Skeet
Play online and complete a Quick Match or Custom Match
Qualify for the finals of every event in an Olympic Games mode campaign
Score ten or more on every target in a 5-shot round in Rapid Fire Pistol, while representing a nation
Earn a Gold medal in every Shooting event, while representing a nation
Unlock all available sporting accessories
Earn 20 medals in a single Olympic Games campaign
Wear an alternative national kit in an event
Perform 10 Power Shots in a Table Tennis match
Win an Online Tournament
Earn the Gold medal in every event of a medium or hard Olympic Games mode campaign
Earn 9 Challenge Stars in a single Challenge Set
Earn a Gold medal in The Olympic Games mode
After using a Retry Token, get a better result than before, and finish in the top 3
Qualify for the finals of an event in The Olympic Games mode
Win an Events Mode session with four players competing
Beat a World Record
Complete a Challenge Set with 4 players
Receive a perfect ten from one of the Judges in Diving
Earn a Gold medal in each of the 5 types of Swimming event
When two or more players are introduced all together for a race, be the one who emotes first
Earn a Gold medal in every Throwing event, while representing a nation
Touch the bar in a High Jump and still clear it successfully
Earn a Gold medal in each of the 4 types of Track events
Complete a multiplayer game, while representing a nation
Touch the last hurdle and win a medal in 110m Hurdles
Create and play through a custom playlist