"Hope Torture"
The best possible act toward one who loves you is to love him/her back.
However, if you cannot do so, then the next best thing is to give him/her the despair.
In another word, let him/her understand clearly, in no uncertain terms, that there is no possibility to become lovers.
Because, if you don’t, he/she will hang on to the small hope and wait for you, while being unable to open his/her heart to others.
However, humanbeings, by instinct, have desire to be loved by as many others as possible. Therefore, although he/she is not the one you like, you still want to be loved by him/her.
Calling while drunk and saying “I called to hear your voice”; continue to date someone whom you have no intention of commitment, but simply it’s OK; using the excuse of family issues, unable to forget ex-boyfriend/girlfriend, or to concentrate toward work, when the real reason for breaking off is because you dislike him/her: all these are acts that give “hope” to the others involved.
And, such acts can hurt the person seriously by leaving wants, frustrations, and obsessions in his/her heart.
I call such acts the “Hope Torture”.
So, if possible, let’s not torture the one who loves you in these manners.
If you cannot love him/her, the least decent thing you can do is not to give any hope, so that he/she can go in search of others who can.