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