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