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