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