Careless driving offences can result in anywhere between 3 and 9 points being added to a licence. See here:
http://www.direct.gov.uk/en/Motoring/DriverLic ensing/EndorsementsAndDisqualifications/DG_100 22425
(If a driver accumulates 6 points within 2 years of first passing their test, their licence is revoked and they have to re-apply for a provisional licence and re-take their driving test. Thereafter the normal rule applies whereby 12 points, all gained within 3 years, normally leads to disqualification).
In the majority of cases, the minimum 3 points are handed out.
Additionally, careless driving is likely to result in a fine. The size of this depends on the seriousness of the offence and the offender's ability to pay but it's likely to be in the range of �100 to �250. On top of that there will be court expenses of, perhaps, �60, and a �15 payment to the victim compensation scheme.
Threatening behaviour might either be dealt with by a fine (of, perhaps �100 to �250) or an order for punishment within the community (e.g. unpaid work), or possibly both. In respect of someone who has already displayed a tendency to aggression and is now before the court for threatening behaviour, it's possible that the court might order attendance at an anger management course. Such a course typically involves several initial one-to-one meetings with a probation officer followed by weekly group meetings (probably each 2 hours long and lasting for perhaps 12 weeks), followed by further one-to-one meetings.
Chris