The worst thing a person can do other person is neglect.

You can be angry with some one and express it. You can hate some one and express it. You can be disgusted with some one and yet express it.

But if you neglect some one, then the wounds run much deeper than any thing else. I am not sure why. (1)

You can shout at some one, say sorry and move on. You can even hit some one say sorry and move on (I dont recommend this though). But you cant just neglect some one, for a long time, and then still hope to build a relationship with them in future.

Neglect is basically questioning some one’s mere existence and its impossible not to feel extremely insulted and depressed because of it.

Be careful with this powerful weapon, you might burn down bridges which you dont want to.

(1) - Very quick research shows me that know one has ever attempted to study neuro-behavioral pattern when exposed to neglect, or tried but I am not able to google the findings. And since neglect is not really expression of any emotion, it is perhaps difficult for brain to process it and hence it leaves a deeper mark on emotional processing of the individual. Animals are also observed to react to it. My personal, thoroughly un-scientific observation is - couples which often quarrel end up having better relationship than couples who use neglect to express then anger/frustration/disagreement (silent treatment etc).