Hardhearted laws succeeded — around half of them (8)
I believe the answer is:
ruthless
'hardhearted' is the definition.
(I've seen this before)
'laws succeeded around half of them' is the wordplay.
'laws' becomes 'rules' (rule is a kind of law).
'succeeded' becomes 's' (genealogical abbreviation).
'around' means one lot of letters goes inside another.
'half of' suggests halving the letters.
'rules'+'s'='ruless'
'them' cut in half is 'th'.
'ruless' going around 'th' is 'RUTHLESS'.
(Other definitions for ruthless that I've seen before include "Brutal" , "nasty" , "Callous" , "Hustlers can be without mercy" , "Without mercy or pity" .)