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