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