Change the gender of the protagonist.
I know, I know, even this has been done before. But this is the quickest way to change a whole lot in a short amount of time. This has the potential to change nearly every relationship as you go through your rewrite, and therefore change a whole lot of what is going on.

Remove one of the important characters from the protagonist's life and replace them with someone else.
If the mother is most important, replace that relationship with a best friend, or a lover, or a sister. This will change the dynamic with the most important person, which changes a lot of the relationships.

Make the strength for the protagonist a weakness, and a weakness a strength.
This can create a whole lot of fun, and will force a lot of rewriting. So, it will change the story quite a bit.

These are not the only ways things can change! Get creative.

Any of these changes can also be made to the antagonist to change up the story line. So, to be absolutely sure your idea is truly different, pick at least one change for the protagonist, and at least one change for the antagonist. Then document the changes as you go through the rewrite and clean up all loose ends.