A foreign criminal insulted others online without restraint (12)
I believe the answer is:
uncontrolled
'others online without restraint' is the definition.
I can't tell whether this definition defines the answer.
'a foreign criminal insulted' is the wordplay.
'a foreign' becomes 'un' ('a' translated into French).
'criminal' becomes 'con' (abbreviation for 'convict').
'insulted' becomes 'trolled' (I can't justify this - if you can you should believe this answer much more).
'un'+'con'+'trolled'='UNCONTROLLED'
Can you help me to learn more?
(Other definitions for uncontrolled that I've seen before include "Without restraint or regulation" , "Not regulated" , "Out of hand" .)