soma soul damage

this is something i dont understand i see people useing the same souls i have but can do about 100 damage or 7 damage more than what i can do and my stuff is as high as it can go does this have something to do with the number of souls i have or do i need all 100% of the souls maxed out or just one of each cause i really would like to know so i can effectively back up my dual valmanways