The Three C's of Limitations

The more powerful your magic is the less crucial to the story it needs to be. If we start introducing either cost consequences or countermeasures we can actually balance that out. A really simple countermeasure would be if for example somebody's magic power reflected damage. That seems like a minor thing but that just negates everything that one punch man can do. And we now have an interesting story. As he this person with ultimate power has to figure out a way to deal with this person who will one shot him as soon as he one shots them.