This is an exhilarating phrase but it is difficult to translate in English.
Can you imagine the scene that heros/heroins knock down many enemies one after another.
This phrase implies that situation above.
I’ll explain it.
快=It literally means “exhilaration” when used alone. Often times this Kanji is connected another Kanji.
刀=It simply means “sword”.
乱= It implies “shitstorm”.
麻= It metaphors “thread”.
When these 4 characters above are connected, it creates wonderful meanings like a hero story.
快刀乱麻
This phrase explain a situation that someone cut tangled thread exhilarating one after another.
In other words, it implies to defeat many enemies or to solve a lot of problems.
If you are interested in these Kanji, you may simply copy them from this website and use them as you please. Make them yours!