Here is the full list of all 12 Apex Legends achievements. It takes around 60-80 hours to unlock all of the achievements on Windows.
Become the Kill Leader
Win a game as an offensive character
Win a game as a recon character
Win a game as a defensive character
Respawn a teammate
Equip a fully kitted weapon
Be the Jumpmaster 5 times
Win a game as a support character
Reach player level 50
Equip a legendary Helmet and Body Armor at the same time
Deal 5,000 damage with 8 different Legends
Win a game with 8 different Legends