Excuse me if this is an old thread, but I just woke up and thus time means nothing to me.
From a High Elf perspective, Tyrion and Teclis would definitely be right up there; the former is Aenarion reborn, the latter obliterated Malekith's physical form and is widely considered the most powerful living mage (he also taught the Empire the schools of magic). I think though that in a world like Fantasy, there is no single 'most powerful' - almost every faction/race has their own 'demi-god' warrior/mage.
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