Many terms are possible depending who you are talking about. White trash, scum, redneck, riff-raff...

where X could be anything from arsehole to cunt to git to twat (or whatever else you feel like)

You know 'asozial' was one of the categories used by the Nazis for 'undesirable' people (i.e. those who could be sent to be murdered in concentration camps)? So I would think twice before using this term. Speaking of which, the term 'gypo' is also highly pejorative. Makes you sound like someone who would support the British National Party (far-right neo-fascist party in the UK).

If you had to find a translation for this word in the sense of Chrissy's example, in the UK context this would probably be 'asbo' (from 'Anti-social Behaviour Order', i.e. a court order which mandates people who have displayed anti-social behaviour to stop doing whatever they were doing). This is now often used as a noun, or in compounds, e.g. 'The asbo-kids were round the back again today'.