How to remove animation from duplicated object? I duplicated an object and then added an animation to one of them, the animation appears in both objects in the outliner, also in the dope sheet and graphic editor and I can't remove the animation from one of them without removing it from the other.

So, I removed all the key frames and the animation from the dope sheet and graph editor, also unlinked the animation in the outliner but the animation is still showing in the outliner and every time I try to ad a new one, it becomes shared by both objects again.
That's because you didn't duplicate the object (which is done by pressing Shift + D), you instanced it (done by pressing Alt + D).

The difference is that, when using the second method, all of the object's properties get linked to another's, so, editting one will result in all being modified.

To unlink a object, you use Make Single User, by pressing U, in Object Mode, which will give you a list of possible data to unlink. As you seem to only want independent animations, then choose Object Animation on the list that shows up