I have factory-reset my mobile, and had already scanned with antivirus for adware, which it found but it couldn't remove. What should I do?
The only method that is left if it the adware truly resides in your phone memory is to flash your phone with its original ROM.
You can also try full resetting it after removing your memory card, sometimes adware comes from the files which were saved on memory card.
Try out a full wipe, don't worry, you can get out of this problem.