Pro Needed - Fable II
is an awesome thread created by pezza888
. You can find "pros" here to help you out with a variety of achievements on Fable II.
I happen to be the "pro" to help you with this achievement. As others have stated, you can unlock this achievement by "seeing another Hero do so." So I am volunteering myself to be that other Hero. Send me a message here on TA or online and I'll help you out as soon as I can.
Alternatively, you can go through the game yourself. Just be sure to save the game after entering the Spire but before you make a selection. This way you can dashboard after earning one achievement, and reload your last save to earn another. Repeat this once more and you'll have all three ending achievements.