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