“The different accidents of life are not so changeable as the feelings of human nature. I had worked hard for nearly two years, for the sole purpose of infusing life into an inanimate body.” (Frankenstein) Chapter 5. He spent so long to make this body have life, he was responsible to watch it and teach it how to survive in the civil world. Everything it did was his responsibility.
“My person was hideous and my stature gigantic. What did this mean? Who was I? What was I? Whence did I come? What was my destination? These questions continually recurred, but I was unable to solve them.” (The Creature) Chapter 15. Frankenstein didn’t even teach the creature about what he was or how to talk, act, eat, or anything.
"I do refuse it," I replied; "and no torture shall ever extort a consent from me. You may render me the most miserable of men, but you shall never make me base in my own eyes. Shall I create another like yourself, whose joint wickedness might desolate the world. Begone! I have answered you; you may torture me, but I will never consent." (Frankenstein) Chapter 17; Frankenstein realized that making another monster wouldn’t be smart, it would just cause him to have another creature to be responsible for walking around that he couldn’t take care of.
“The name of my unfortunate and murdered friend was an agitation too great to be endured in my weak state; I shed tears. "Alas! Yes, my father," replied I; "some destiny of the most horrible kind hangs over me, and I must live to fulfil it, or surely I should have died on the coffin of Henry." (Frankenstein) Chapter 21; Frankenstein just got off for the murder for his friend, and was in a very weak state, he knows that he needs to get home and protect his family from the wickedness that he has caused.
"Alas! My father," said I, "how little do you know me. Human beings, their feelings and passions, would indeed be degraded if such a wretch as I felt pride. Justine, poor unhappy Justine, was as innocent as I, and she suffered the same charge; she died for it; and I am the cause of this—I murdered her. William, Justine, and Henry—they all died by my hands."
(Frankenstein) Chapter 22; Frankenstein is taking responsibility for the deaths of his loved ones at the hand of the monster he created.
"Oh! Peace, peace, my love," replied I; "this night, and all will be safe; but this night is dreadful, very dreadful." (Frankenstein) Chapter 23; he knows that the monster is coming and he doesn’t want to worry Elizabeth so I just tells her to be calm and he will take care of it. He took it into his own hands to battle and kill the monster, though the monster came for Elizabeth instead of him.