Night shades

So I know it’s by choice between attack and magic attack.. my question is based on the fact I see some videos of end game stuff and people getting 9999+ with weapons like luigis hammer and so on. Am I doing something wrong?? Am I missing something? My luigis hammer doesn’t even do equal or above 9999 which is why I find this somewhat frustrating and wanna fix a possible error(s), any help would be great thanks!