Do I need to get all the Red Dead Redemption achievements to get 100%?
You do not need every single XBL achievement in order to get 100% completion in Red Dead Redemption. You need to do the following:
- Complete all 57 story missions
- Purchase all 5 rare weapons
- Do the 3 Nightwatch jobs and 2 Horsebreaking jobs at least once
- Unlock all 9 Outfits
- Purchase all 13 player houses
- Complete all 7 gang hideouts
- Complete 20 bounties, doesn't matter if you kill or capture. You need 8 in New Austin, 8 in Mexico, and 4 in West Elizabeth.
- Win at all 6 minigames at least once
- Discover all 94 map locations
- Complete all ranks of Survivalist, Treasure Hunter, Master Hunter, and Sharpshooter challenges (rank I and II)
- Complete 18 Stranger missions (though the I Know You one doesn't count towards this, as it is potentially missable)
If you're signed up on Rockstar's Social Club website, it keeps track of what you've completed, which I've found to be a great help. It's kind of slow in keeping synched though, but it's awesome for reference.