In my understanding Kai-hen wizard means wizard killer, right?

I don't understand the title as well, maybe a mistranslation?

no, the title is actually "Kaihen no Mahoutsukai", kaihen is a bit hard to directly translate, it's something about world change/ changing world, mahoutsukai is wizard, so the title is "Wizard/s of world change/changing world (or whatever tf is more accurate

rather that "kai-hen wizards", maybe it's more accurate to use "wizards of kai-hen" instead

So it may means that mc is a wizard who can change the world of wizards / change the understanding of wizards, maybe something like this in the story?