Word of Life

Harry potter's last spell against voldemort is a simple expelliarmus, Expelliarmus disarmed Voldemort and rebound Voldemort's Avada Kedavra and destroy Voldemort.

Just think about that 

Expelliarmus vs Avada Kedavra

Which one is more powerful at first glance ; Avada Kedavra obviously but Expelliarmus wins at the end of the day.

You don't need one of the most powerful skills to win in life you just need one skill that you are the specialist.