Mysterious assassin tied to Ethan's past.
Gabriel is Ethan's personal and operational adversary.
Ethan recognizes Gabriel as a shadowy figure from his pre-IMF past and later fights him on top of the train.
Gabriel directly causes Ilsa's death.
Gabriel declares that either Ilsa or Grace will die and later kills Ilsa in Venice.
Grace is a direct target of Gabriel's scheme.
Gabriel states that he will possess the completed key if either Ilsa or Grace dies, and he later incapacitates Grace.
Gabriel treats Paris as a compromised subordinate and threat.
Gabriel tries to kill Paris because the Entity predicts that she will betray him after Ethan spared her life.
Their attempted negotiation ends in Gabriel's betrayal and murder.
Denlinger meets Gabriel on the train to discuss an alliance with the Entity, but Gabriel kills him after learning the secret of the Sevastopol chamber...