There are several reason that Victor Frankenstein is (ironically) less human than the monster he has created in Mary Shelley's Frankenstein.
Victor defies the laws of society and religion when he steals dead bodies from graveyards—for cemetery's are hallowed (holy) ground. He also defies the laws of religion when he attempts—and succeeds—in imbuing inanimate flesh with life. He is playing God. Once Victor brings the creature to life, he refuses to assume responsibility for what he has done. He is just like a parent, and yet he does not care for the creature as a parent should, but abandons this defenseless being to the threats of society and the world. In Chapter Ten, now educated and able to converse with Victor, the creature chides the scientist for what he has done:
...you, my creator, detest and spurn me, thy creature, to whom thou art bound by ties only dissoluble by the annihilation of one of us. You purpose to kill me. How dare you sport thus with life?
I believe that Victor is also monstrous in keeping his secret to himself. Had he been honest with friends and family, he might have saved most of those he loses to the monster's fury.
Then the monster says:
Do your duty towards me, and I will do mine towards you and the rest of mankind. If you will comply with my conditions, I will leave them and you at peace; but if you refuse, I will glut the maw of death, until it be satiated with the blood of your remaining friends.
Victor knows immediately that he can save his friends if he makes the monster a companion. One of the most devastating things about the creature's life is that he is so alone. Victor created this situation when he fled from the creature the night he created it. However, now he can make it right by giving the monster someone who will not reject him so that he does not have to live alone for the remainder of his existence.
However, Victor now feels remorse for his earlier actions. Had he been as thoughtful before, he would never have pursued his experiments. And if Victor's reasoning that creating another creature would be a further threat to mankind, he at least owed Elizabeth and Clerval a chance to know they were in danger.
The saddest part of the story is that Victor never realized that he might have saved everyone—William, Justine, Clerval, Elizabeth, and Alphonse—if Victor had agreed to befriend the creature. In this way, he would never have had to decide whether it was safe to create a companion for the monster—who only asked for this because he was so lonely. At the side of his dead creator, the creature tells Walton:
Yet I seek not a fellow-feeling in my misery. No sympathy may I ever find. When I first sought it, it was the love of virtue, the feelings of happiness and affection with which my whole being overflowed, that I wished to be participated...Once my fancy was soothed with dreams of virtue, of fame, and of enjoyment. Once I falsely hoped to meet with beings who, pardoning my outward form, would love me for the excellent qualities which I was capable of unfolding. I was nourished with high thoughts of honour and devotion...I cannot believe that I am the same creature whose thoughts were once filled with sublime and transcendent visions of the beauty and the majesty of goodness...I am alone.
Victor's selfishness and inability to care for the creature he created, breaking God's and society's laws, and failing to protect his loved ones make Victor a monster.
I will keep my response brief with points to consider...
Frankenstein's unwillingness to accept his creation makes him less human. Examine the repetitive tone and word choice used when Frankenstein refers to the creature throughout the novel.
Ulimately, it is Frankenstein's lack of acceptance which forces the creation/creature to seek both acceptance and vengeance.
Consider all the deaths and pain caused by Frankenstein's selfishness. Consider Frankenstein's obsessive behavior. Consider Frankenstein's subtle decay which occurs chapter by chapter.
Use strong quotes to support your assertions. Good Luck!