How did Victor feel upon his successful attempt at the reanimation of the human flesh?
In short, he is horrified. He cannot fathom the thing he has created, and he described his terror in this way:
I had desired it with an ardour that far exceeded moderation; but now that I had finished, the beauty of the dream vanished, and breathless horror and disgust filled my heart. Unable to endure the aspect of the being I had created, I rushed out of the room, and continued a long time traversing my bed-chamber, unable to compose my mind to sleep.
He is discovering that what he has spent years creating is now his worst nightmare. Of course, this is all based upon its physical appearance; the creature is, in reality, quite articulate and sensitive. Victor runs from his creature, locks himself in his room, where he falls asleep. He suffers a terrible dream in which he imagines Elizabeth turning into a corpse before his eyes, & upon waking, he witnesses the creature again:
I beheld the wretch -- the miserable monster whom I had created. He held up the curtain of the bed; and his eyes, if eyes they may be called, were fixed on me. His jaws opened, and he muttered some inarticulate sounds, while a grin wrinkled his cheeks. He might have spoken, but I did not hear; one hand was stretched out, seemingly to detain me, but I escaped, and rushed down stairs.
This description is filled with words of negative connotation. "Wretch", "Miserable monster", "inarticulate"- these all point to Victor's perception of the creature as something to fear and hate. He even describes his need to "escape" although the creature has not made any sort of aggressive move toward him. Thus, Victor's ultimate quest for knowledge has dissolved into a regret that will haunt his life.