Volume 3 of the novel Frankenstein ends with Walton's final letters.
In this last part of the story Victor finds out that Walton had been recording the events that he narrated. As he found this out, he requested to see what Walton had written down. Victor proceeded to correct and enhance some of the notes.
What he enhanced was the intense anger that he felt against the creature. He wanted to ensure that the story explained how dangerous the creature was, and how much Victor hated it.
At the end, Victor told Walton
'Since you have preserved my narration,' said he, 'I would not that a mutilated one should go down to posterity.'
"Mutilated" means injured or imperfect. This quote shows Victor's concern that the world to know exactly what he did and that he wants to warn the world about it. He wanted to express clearly how wretched the whole situation was, and how sadly the story ended.