8 of the secret achievements in Red Dead Redemption are storyline related. There’s That Government Boy, Land of Opportunity, Sons of Mexico, No More Fancy Words, A Savage Soul, The Benefits of Civilization, Into The Sunset and Nurture or Nature, all of which you will complete simply by following the main quest line.
The actual secret achievements that are not story related are:
Dastardly – I mentioned this one in a previous post that you get for hog-tying a woman and leaving her on the railroad tracks. It only counts if you see her get hit by the train.
Spurred Into Victory – You get this for completing 20 storyline quests with the same horse.
Heading South On A White Bronco – You have to commit a crime and then escape the law on the Hungarian Half-Breed horse. I believe it only counts in single player mode.
Manifest Destiny – You have to kill all the Buffalo in the Great Planes.
I was really hoping that one of the secret achievements was to break one of every horse in the game, which I have been trying to do, hehe, but unfortunately it isn’t. I will stop wasting time doing that I guess and get back to trying to beat the game!