Satele. She almost solo'ed Malgus. My sorcerer solo'd Thanaton but needed a group of 4 for Malgus. Therefore, Satele>Thanaton.
If the memory serves me right, Satele actually needed help from both her master and Jace Malcolm to survive her clash with Malgus so I fail to see how she solo'ed him.
Remember The Return and Hope trailers? Watch them again.