Evade the US Marshals while riding the Hungarian Half-Bred horse in Single Player.

Before you start this you will need to break a Hungarian Half-Bred (white horse with a dark face). Once you have broken the horse you can then buy the deed for that specific horse, activate the deed from your satchel and you can call the horse you require.

If you don't want this to affect your current progress I suggest you save in one of the empty slots. Stock up on ammo and make your way to any town. You will now need to start killing law enforcement, after you have killed 20 law enforcers you can now leave town and lose your wanted level. You're now going to need to ride around for a while until a notice pops up on your screen telling you the US Marshals have found you. One this happens you need to outrun them and escape. Evading the Marshals won't be as easy compared to outlaws, law enforcement or posses as they are highly skilled.

You can evade them by either killing them or running and loosing your wanted level.