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