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