how to get rid of a spy software on a cell phone

[abbaqa1]

is factory reset enough to delete a spy software on a cell phone???? or some software ll still work?
does factory reset makes the cell data ( pics , videos , passwords ) unrecoverable or we should use a data shredder for it, if we need to use then tell me the best data shredder plz.
i used a data shredder with 7 passes but it made me android extremely slow after the shredding was done and even after factory reset it is still so slow can u help?

 

[Alabalcho]

What do you mean as "shredding"? Did you connect your phone to a computer where this "shredding" software was running? You did not have to do that.

"Factory reset" usually wipes everything on your phone - contacts, messages, photos, music etc. If you did not install custom ROM, this should get rid of any additional apps.