Cannot delete old Comcast emails from my Outlook.com account.

I need to delete the imported Comcast.net emails. Somehow they imported into Outlook.com more than once and now I have 100k emails which brought my storage to the max and no one could email me. I deleted the Comcast.net account from Outlook.com but now I can't seem to be able to delete all the messages. I have tried to delete the folder and separately the messages in the folder and neither has worked. I also now moved the whole folder into the deleted folder but now it's just sitting there. How can I get rid of all the imported emails??