שופטים, פרק ט׳, פסוק נ״ג

As Abimelech advances toward the fortified tower, his violent campaign comes to a sudden and decisive end. From the roof above, a woman among the barricaded defenders hurls a heavy object down at him, striking him unexpectedly and perhaps with remarkable precision [ביאור שטיינזלץ].

The object she drops is a dense fragment of an upper millstone. In its regular use, this top stone sits and rotates upon a lower base stone to grind grain. A broken piece of this heavy upper stone is what plummets toward Abimelech, landing with a devastating force that completely crushes and shatters his skull [רד״ק, מנחת שי] [מצודת ציון].

This fatal blow carries deep poetic justice. First, it serves as the direct fulfillment of Jotham's earlier curse, which warned that destruction would emerge from the people of Shechem to consume Abimelech, culminating here in a woman causing his ultimate downfall. Furthermore, there is a clear measure-for-measure punishment at play. Abimelech had ruthlessly murdered his brothers upon a single stone, and in perfect alignment with his crime, his own life is violently ended by the crushing weight of a single stone [מלבי״ם].