A little like 'face only a mother could love', but worse. Someone whose appearance instantly provokes immediate thoughts of very violent acts. You'd probably be doing them a favour, in fact.
as per "that (insert name here)'s got a face only a fist could love"
Examples:
Sonia off Eastenders
Any Liverpool fan
The sort of bloke who walks around town without a shirt on. (classless scum)
17👍 3👎