Caledor Dragontamer. Forged the ''pact'' between Elves and Dragons, gifting the Elven Race with arguably the most fearsome tools of slaughter, of all time. Also teaching the Elves the way to use magic offensively, and defying Aenarion to conjure and cement the Vortex upon the Isle of the Dead, trapping -or drawing in- massive quantities of raw magic and preventing the Ruinous Powers free will over the mortal plane. In essense, this guy ''saved the world'' despite the horrendous cliche.
He`s not -technically- dead; but my vote for a still-living wizard would be Morathi. She created the Lore of Dark Magic, and has perfected it from her several-thousand year banishment from Ulthuan. Even Malekith is regarded as he inferior in terms of the magical art and I`m sure she would be able to slay Teclis in a sorcerous duel.