The Great Commentary of Cornelius a Lapide explains:
Ver 27 - But those mine enemies (the jews, His citizens, who would not have Him reign over them) bring them hither - to my tribunal in the valley of Jehosaphat and Jerusalem - and kill them before me. In the Greek, "Kill them before my face." Our Lord alludes to those victorious kings who slew and destroyed their conquered rebels. By this destruction Christ signifies the extreme judgemntof the Jews and His other enemies, and the town condemnation to eternal death in Ghenna, and that a living and vital death, where they will be perpetually tormented by death-dealing flames, and yet will never die. Our Lord alluded to Titus, who slaughtered the conquered Jews. He describes to the letter the condemnation of the Jews, and the Ghenna which He has appointed for them when He shall return from Heaven to judge and condemn them and the reprobate.