A low-life (numpty). Someone who you consider to be lower than the hairs of your arse. To look at someone as if you would have to scrape them off the bottom of your shoes.
A Chav or Chavette is a complete Bumfinkal, because he/she believes they are gangsters or better than they actually are, when in fact they are a menace and a drain on society. What a waste of oxygen that complete Bumfinkal is.