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