"According to the Last Defenders comic.Daimon Hellstrom is more powerful than Dr.Strange "could hope" to be...so I think there is a good chance he wins.I also just seen him kill and alternate reality version of Hyperion in the same comic."
He is a beast!
Hellstorm IS more powerful than Mephisto. He's taken Black Halo meaning he is Lord of his realm of Hell PLUS all the power and abilities he had before his ascension (or descension if you will). His powers ARE NOT limited to his realm (as he was able to send a warehouse full of Angels to Hell). He was breed to be the Anti-Messiah for the Dark Lords but since he is also a man he isn't has limited as they are on Earth. Hellstorm in a horrificly, bloody, short and brutal victory over BH.