To destroy or corrupt — used of moral corruption before the Flood (Gen 6:11-12), of God's destroying judgment, and of human ruin. The 'destroyer' in Egypt at Passover is the same root.
The Flood narrative uses shachath repeatedly: the earth was corrupt, all flesh had corrupted its way (Gen 6:11-12). God's response to corruption is the flood — destruction restoring creation order.
The 'destroyer' (mashchit) of Passover (Exod 12:23) shares this root. God both uses and restrains destruction. The incarnation brings the Savior into a world under shachath — corruption — to reverse the ruin of sin.