Here is an explanation of the source of power of the Sword of Power:
Here is the Sword of Power in action:
Here is an explanation of the source of power of the Sword of Power:
Here is the Sword of Power in action:
Amongst the three, it should be He-Man's.
If we are talking about pure physical damage, The Shining Knight's enchanted sword can literally cut through anything (unless there are other similar swords that can cut through anything as well)
If we are talking about the 'greatest sword of ALL', then it would be the Sword of Superman, no doubt.
CB's Excalibur + Amulet would be a close 2nd, imho.