Why Did Victor Destroy The Female Monster?

In chapters XVII-XXI of Mary Shelley’s novel, the monster requests Frankenstein to make a female companion for him. The monster explains, “You must create a female for me [...] for my being”. When Frankenstein refuses, the monster starts to threaten and reason with him. He says, “...instead of threatening, I am content to reason with you. I am malicious because I am miserable”. The monster convinces Frankenstein by using his loneliness as the reason he is so cruel and dangerous to the human race. The creature also goes further as to promise to move far away from continental Europe to the wilds of South America.
Doctor Frankenstein reluctantly agrees to the monsters request for a female companion and starts the process in Scotland. After a terrible fit of anger and guilt from a flashback to three years ago when he was in the same situation and created a monster that caused misery to himself and others, the doctor destroys the half finished female monster in front of the monster. As seen in the quote from the novel “I had before been moved by the sophisms of the being I had created; I had been struck senseless by his fiendish threats: but now, for the first time, the wickedness of my promise burst upon me; I shuddered to think that future ages might curse me as their pest, whose selfishness had not hesitated to buy its own peace at the price, perhaps, of the existence of the whole human race. I trembled, and my heart failed within me; when, on looking up, I saw, by the light of the moon, the demon at the casement”, it is evident that Victor will now be responsible for any actions taken by the monster in retaliation for Victor's broken promise. However, this also shows Victor’s understanding of his responsibility. He feels it would be best for the world if he did not make another monster, after seeing the destruction that has already been caused.
This causes the monster to look for revenge and threatens, “It is well, I go; but remember, I shall be with you on your wedding-night”. The monster clearly felt strong anger towards his creator and wants revenge. After this threat, the monster disappears into the night, leaving Frankenstein slightly flustered but not enough to go after him.