Good idea Stealth. When PoD first came out people were arguing that he was one of the most powerful Force Users of all time (making peoples top 5 lists) and certainly one of the most powerful Sith (people typically had maybe NJO Luke, DE Sidious and Nihilus above him, with people like Exar Kun on the same level). Since RoT and DoE came out however people seem to have collated all 3 books into one story, and seem to be under the illusion that his learning curve from PoD to RoT was much smaller than it actually was. He was already a beast by the end of PoD, and aside from the orbalisks, and the rain dance feat the improvements from PoD to DoE really weren't that big.
Well Malgus is also a beast. His lightning owned a Jedi (who has just collapsed two buildings on Malgus with TK) and blew holes through his chest, while injured. His TK has killed Jedi with pushes, shattered large statues and pillars and he blew the rubble from two buildings off of him after holding it up. He smacked the Strike Team in TOR around with the Force and that team was either made up of the Imperial or Republic TOR characters. At the end of Deceived Malgus achieves a state of oneness with the Dark Side, vastly increasing his power.