Dictionary

A destructive capacity that exceeds that needed to destroy an enemy; especially with nuclear weapons.

(by extension) An unnecessary excess of whatever is needed to achieve a goal.

Example: 24 hours of TV coverage of the US election verged on overkill.

An unnecessary excess of disposal because of too high criteria of inspection.

To destroy something with more (nuclear) force than is required.

To dispose of too many items because of too high criteria of inspection.

To do something excessive to achieve a goal.