enforcer

Short definition from Wiktionary

Noun

1. 1
   One who enforces.
2. 2
   A hired strongman, especially working for the underworld.
3. 3
   The member of a group, especially of a gang, charged with keeping dissident members obedient.
4. 4
   A battering ram used by the emergency services for gaining access to locked premises.
5. 5
   A player who physically intimidates or confronts the opposition.