How does hate become a prime motivation for both Victor Frankenstein and his monster?
I can find obvious answers by describing the events in the novel, but I am after maybe something a little more subtle and something that might differ from everyone elses answer. I will be grateful for any assistance. Thanks.
For Victor, the monster was supposed to be his crowning achievement. He had worked long and hard to create the creature, walling himself off from friends and family. However, once he succeeded in bringing the creature to life, Victor found that it was ugly and he abandoned it. Then, ignoring the fact that he left the creature to fend for itself, the monster kills his younger brother. From Victor's perspective, this is the ultimate betrayal. Here is is responsible for the creature's life and the creature turns on him and begins to kill his family. In the end, the creature has killed not only William, but Elizabeth, Henry and the stress of all this lead to the death of his father.
The monster, on the other hand, is left totally alone by Victor. From his own reading, he discovers what a creator should do and is angry at his abandonment by his creator.He is probably also angry at the way his creator made him because others see him as ugly. However, the greatest betrayal the monster sees is Victor's destruction of his "bride". He can no longer hope for any true companionship and his true hatred for Victor begins. The monster kills Victor's best friend and then Victor's wife because Victor had killed what he had hoped would be his best friend and wife when Victor destroyed his bride.
Some critics see the creature as Victor's "shadow" self ... that part of each of us that we are not always consciously aware of that contains things that may be hidden from ourselves:
"It is everything in us that is unconscious, repressed, undeveloped and denied. These are dark rejected aspects of our being as well as light, so there is positive undeveloped potential in the Shadow that we don’t know about because anything that is unconscious, we don’t know about." (from Web site below)
Of course, when Victor first sees what he has done, he commits his major mistake: he fails to love what he has given "birth" to.
It's clearer for the creature: he is born loving, without the "nurture" that might affect most of us --- he is looking for love and it is not returned. So he strikes out in response; not all that unnatural or surprising.
You might want to do some further reading about Jung's "Shadow Self"; there are many sources on the Internet.