Things that are a total loss — really worthless or damaging — are dross. That gunk between your teeth that comes out when you floss? You could call that dross. No one wants it, and it's harmful if it stays.
While dross is a noun for stuff that's physically left over or useless, like the nonmetallic stuff left when metal gets refined, it's also used for people and forms of art. A really bad movie can be called dross, and a low or despicable person can be dross. Debris, or trash, is another form of dross. "Searching the backyard for unexploded fireworks — the dross of Chinese New Year celebrations — was a tradition for the kids and a safeguard for the dogs."