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