I don't think there is a lot of doubt that Thor loves his hammer, and he loves to use his hammer. I also don't think there's a lot of doubt that the hammer has allowed Thor to fight out of his weight class on a number of occasions in the past. So Mjolnir has been very good to and for Thor.
But is the opposite true?
Thor, never the most cerebral of characters, has access to a weapon that has shown virtually no limitations. And yet, aside from a very limited number of circumstances, has almost never used Mjolnir to its fullest.
The question becomes, then, what were to happen if instead of pitting Thor against his rogues and rivals if you instead gave Mjolnir to someone else. Someone more cerebral. Someone who also understands Asgardian magic and its potential. Someone who has always wanted Mjolnir.
Someone like...Loki. Let's say you lifted the worthiness requirement and gave Mjolnir to Loki to play with for six months to learn all of its capabilities. Then you bring him back and have him do battle with some of Thor's toughest opponents. Would Loki with Mjolnir be even more powerful than Thor with Mjolnir?
Let's find out.
Loki with Mjolnir vs.
Beta Ray Bill