Ensure Origin is fully closed by clicking the Origin Menu and selecting Exit.
Delete the following folders:
All the files and folders in the Origin folder, except for LocalContent - Found in C:ProgramData
All files and folders found in C:Users\AppDataRoamingOrigin
All files and folders found in C:Users\AppDataLocalOrigin
Note: These folders are hidden by default, and the player will need to un-hide to be able to locate them.