Here is the full list of all 22 Command & Conquer 3: Tiberium Wars achievements worth 1,000 gamerscore.
Scrin Campaign Finished with Bronze medal and Bonus Ribbon
GDI Campaign Finished with Silver medal and Bonus Ribbon
Scrin Campaign Finished with Silver medal and Bonus Ribbon
Scrin Campaign Finished with Gold medal and Bonus Ribbon
Complete all of the single player campaigns.
Completing the GDI TOW: Washington D.C.
GDI Campaign Finished with Bronze medal and Bonus Ribbon
Nod Campaign Finished with Silver medal and Bonus Ribbon
Nod Campaign Finished with Bronze medal and Bonus Ribbon
Nod Campaign Finished with Gold medal and Bonus Ribbon
Play MP for 100 hours
Lose to someone Ranked 20 places below you in a MP Ranked Game
Complete the Nod campaign
Completing the GDI and Nod campaigns
Complete the GDI campaign
Press the A button 2047 times, the year the game takes place
Complete Boot Camp Mission
Gather 100000 tiberium in MP games
GDI Campaign Finished with Gold medal and Bonus Ribbon
Negative Achievement: Lose a single player game 3 times in a row
Negative Achievement: Lose 5 MP games in a row
Negative Achievement: Skipping the Tutorial suggestion from SP