Victor waffles on whether or not to comply with the Creature's request for a companion. His indecision rises from his uncertainty as to whether he should have created the Creature in the first place. Here is the breakdown:
Creature (pro): I am so lonely! I harass and murder people out of fear, rejection, depression, and loneliness. If I had a companion as you do, I would be happy and would leave the rest of humanity alone. I would stay in hiding in a cave with my lady monster and never bother you again. You won't even have to look at me anymore. I will keep her with me - it won't be hard because society will reject us both, so she will be inclined to stay with her kind and away from society. Also, you owe me this because you created me with no thought as to how I would be received by the public or even by you, my creator. I should have been your Adam, but instead you treat me as Lucifer, cast into Hell to be sad and alone forever. All I want is someone to love me!
Victor: I regret ever making one of these things - to make two could be disastrous. What if they don't stay in seclusion? What if they go on murderous rampages as a date night out on the town(speople)? I know he's lonely, but maybe he deserves to be lonely for all of the horrible things he's done... all of which are my fault because he's my responsibility. Okay, so say they go into hiding and stay there for the rest of their lives. When will they die? Will they die at all? Are they immortal? WHAT IF THEY REPRODUCE?! I can't be responsible for litters of mini-monsters roaming the earth and killing people just because they can!
In the end, Victor decides against finishing the "companion" and destroys all of his progress to-date. The Creature, who has been creeping around and watching through a window, goes into a rage and swears revenge on Victor's wedding night. That same night, still enraged, the Creature kills Victor's BFF, Henry Clerval.