how to repair a bathroom shower wall with huge holes right through the wonder board

You just discovered why it’s not good idea to use hammer to remove tile, unless you are demolishing entire shower. Best way to repair is to cut out section of concrete board to stud. You’ll have to remove additional tile. But it’s important that this surface by water tight. Don’t want water to get behind the wall! Cut out rectangular section to adjacent studs. You want to ensure board is securely installed. Cut out new piece and nail to each stud. Seal the seams with proper mastic. Re-tile once Board is dry.