Who is the weakest magical character that can beat Dormammu?

Now that Dormammu is written to be more powerful than the Vishanti combined, who would the weakest magic character be that can beat him one on one?

Wong calling the Vishanti was defeaed by Mordo/Dormammu.
http://comicvine.gamespot.com/images/1300-5540997
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http://comicvine.gamespot.com/images/1300-5540999

Old King Thor with the Necro Sword should take care of him.

It would have to be a sorcerer on Dr. Strange/Fates level, and without PIS it would be a huge struggle. Just to give a ballpark figure of how powerful Dormammu is. In the past when Strange defeated him, I had trouble with the victory, because it seemed as though Dormammu foiled himself by holding back. I mean he should have been able to life drain Stephen the minute the fight began.

Necro Thor > Galactus > Old King Thor > Odin

I don't see why Necro Thor wouldn't win, he's stronger than Odin with the Odinforce.

Black Alice.