Why did God have to nail his son to a stake to forgive us for our sins?

I asked this question a few minutes ago and nobody really answered it. WHY IS THIS NECESSARY? If God is all-powerful, then that means he can do whatever he wants. It isn't required that he sacrifice someone before forgiving us (forgiving us for being human). If God is omni-benevolent, then wouldn't be inclined to avoid sacrifice and suffering?