The conclusion of the Virgil's Aeneid is one of the most controversial passages in Western Literature. Some scholars would argue that Virgil was not finished with the epic and that he would have found a less abrupt way to conclude the epic. Numerous other scholars have argued about whether Aeneas should have killed Turnus or should have spared his life.
As soon as his eyes took in the trophy, a memory of cruel grief,
Aeneas, blazing with fury, and terrible in his anger, cried:
‘Shall you be snatched from my grasp, wearing the spoils
of one who was my own? Pallas it is, Pallas, who sacrifices you
with this stroke, and exacts retribution from your guilty blood.’
So saying, burning with rage, he buried his sword deep
in Turnus’s breast: and then Turnus’s limbs grew slack
with death, and his life fled, with a moan, angrily, to the Shades. (A.S. Kline translation)
If we could accept that Virgil intended to conclude the Aeneid in the way that it does end, with the death of Turnus, then we might think that Virgil intended to leave his audience to answer for themselves the question of whether Aeneas was justified in killing Turnus.
A similar sort of question would have to be asked by many in Virgil's Roman audience. When Virgil composed the Aeneid in the 20s BCE, his fellow Romans had just emerged from twenty years of civil war. They had fought against their fellow countrymen. In many cases, they had to decide whether to kill or to spare their fellow countrymen.
I suspect that Virgil intended to end the Aeneid with the death of Turnus, but I like to imagine that it was part of Virgil's brilliance not to answer the question of justification for his audience. This is a question that his abrupt ending suggests they must answer for themselves.