In chapter 5 of Frankenstein we find Victor and the monster finally coming face to face. From what we can see, Victor completely loses touch with his previous ambition the moment he lays eyes on the creature. This is ironic: He is the creator of the creature, the man who put all the dead body parts together, and the architect of all the dynamics that his ambition drives him to do. Hence, we ask, what does Victor really expect to see after the creature comes to life? From his description, we realize that the disgust and anger that Victor feels for the creature is tremendous:
...when, by the dim and yellow light of the moon, as it forced its way through the window shutters, 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 downstairs.
Hence, the first thing that Victor is fixated upon is the eyes of the creature. Eventually he mentions them again in the novel. However, it is not just the yellowy, dead look of the creature's eyes what gives Victor that feeling: Its the fact that those same eyes were looking up at Victor seeking some paternal love, or protection. That combination of tenderness and horror is the real cause of Victor's hatred towards the monster.
Lastly, another thing that Victor hates is the fact that it was he, with his huge ego and airs of superiority, what gave life to such a horrid thing. That is perhaps what he detested the most.
Oh! no mortal could support the horror of that countenance. A mummy again endued with animation could not be so hideous as that wretch. I had gazed on him while unfinished; he was ugly then; but when those muscles and joints were rendered capable of motion, it became a thing such as even Dante could not have conceived.