Killing can be used for Violent. Violent is the opposite of Peaceful. Peaceful is related to Sheep. 
Eye is related to Tear. Tear is related to Part. Part is related to Organ. Lens is a type of Organ. 
Killing --UsedFor--> Violent <--Antonym--> Peaceful <--RelatedTo--> Sheep 
Eye <--RelatedTo--> Tear <--RelatedTo--> Part <--RelatedTo--> Organ <--IsA-- Lens 