If something is flawed, it is spoiled by a mistake, a weakness, or damage. A flawed diamond has a mark inside. A flawed plan has a hole in it — it will not work as written. A flawed argument does not hold when you push it. You can say it of objects, ideas, and people.

With people it is often gentler than “bad.” A flawed hero is brave, and also proud, or kind, and also careless. The work is still worth looking at; it is just not perfect. In reviews, “a flawed but interesting film” is almost a kind sentence: they liked it, with reservations.

A flaw can be a tiny crack or a serious fault. So flawed covers a wide stretch, from “not quite perfect” to “this will break.” The word is ordinary English, not slang. It is simply flaw plus -ed: having a flaw.