The Exorcist III ending explained

What happens

Kinderman shoots the patient's body, which frees what remains of Karras and ends the killings. It reveals that his steady, stubborn compassion was enough to hold against something built to make him despair.

The last image

Kinderman is left mourning, grieving but still believing.

What it says

The film ends on grief, not triumph, because its question was never whether evil can be beaten. It asks whether a grieving, rational man can still believe in goodness. Kinderman's faith is bruised but intact, and that is the answer.