Here is the full list of all 51 Red Dead Redemption 2 achievements. It takes around 200 hours to unlock all of the achievements on Windows.
Earn 70 Gold Medals in Story missions.
Attain 100% completion.
Red Dead Online: Concurrently own 5 horses.
Deliver 5 camp companion item requests.
Red Dead Online: Craft 25 pieces of ammunition.
Red Dead Online: Reach Rank 50.
Red Dead Online: Purchase 5 camp improvements.
Red Dead Online: Achieve MVP 3 times (in a round with at least 4 players).
Red Dead Online: Play 5 Free Roam Events.
Red Dead Online: Successfully counter a rival Posse's Free Roam mission.
Red Dead Online: Accept 10 Free Roam missions from characters around the world.
Red Dead Online: Take part in a Series.
Red Dead Online: Achieve 5 gold belt buckles from awards.
Red Dead Online: Reach Rank 10.
Red Dead Online: Craft 20 items (excluding ammo).
Red Dead Online: Sell 20 items to the Butcher.
Red Dead Online: Form a Persistent Posse.
Red Dead Online: Pick 25 Herbs.
Red Dead Online: Complete a Free Roam mission as part of a Posse with at least 2 members.
Red Dead Online: Complete the Intro.
Survive 3 days holding a bounty of $250 in all states.
Study every animal across all states in Story Mode.
Skin every species of animal in Story Mode.
Find a permanent home for the squirrel statue.
Survive 18 bear attacks and kill the bear each time in Story Mode.
Craft 30 unique items in Story Mode.
Complete one of the Collectable strands.
Find the graves of each of your fallen companions.
Complete the Epilogue.
Complete 'A New Jerusalem'.
Play all mini games.
Spend $5000 across all shops.
Discover the fate of Marko Dragic.
Complete 'Red Dead Redemption'.
Complete all optional Honor story missions.
Complete 10 Stranger mission strands.
Complete 'Goodbye, Dear Friend'.
Catch a fish weighing at least 16 lbs (7.3 kg).
Reach maximum or minimum Honor level.
Complete Chapter 5.
Complete Chapter 4.
Complete a Companion Activity in each camp.
Complete Chapter 3.
Rob or loot $250.
Recover the stash from 4 homesteads.
Complete Chapter 2.
Reach max bonding level with a horse.
Donate $250 to the gang tithing box.
Upgrade each available component for a single sidearm or longarm weapon.
Complete Chapter 1.
Complete 'Enter, Pursued by a Memory'.