Great rundown of Willoughby’s narcissism and cowardly hide and seek with Marianne. I think this illustrates how miniscule his regard for her really is because the entire time he is hiding she is perfectly miserable, waiting for him, asking him for answers and he could have relieved her just by telling her the truth. He could have saved her their cruel meeting and his letter but he really is too selfish to imagine her suffering. Willoughby has a wonderfully charming façade but it hides a monster in that he seems to have absolutely no empathy for anyone other than himself. He had to visit the Dashwoods at the cottage to say good-bye not to assure them in anyway but satisfy his pride:

"It was necessary to my own pride. I could not bear to leave the country in a manner that might lead you, or the rest of the neighbourhood, to suspect any part of what had really passed between Mrs. Smith and myself, and I resolved therefore on calling at the cottage, in my way to Honiton. (Ch. 15)

It does not occur to Willoughby that it might be kinder to Marianne to declare himself (in his letter) a scoundrel with a bow rather than a bluster:

And after all, what did it signify to my character in the opinion of Marianne and her friends, in what language my answer was couched? It must have been only to one end. My business was to declare myself a scoundrel, and whether I did it with a bow or a bluster was of little importance. 'I am ruined for ever in their opinion,' said I to myself; 'I am shut out for ever from their society; they already think me an unprincipled fellow, this letter will only make them think me a blackguard one.' (Ch. 44)

But, what else could be expected from a man who believes Marianne’s last thoughts on her deathbed will be of him rather than of her life or family? From Ch. 44: “and dying, too, believing me the greatest villain upon earth, scorning, hating me in her latest moments. However Willoughby was wrong. From Marianne’s feverish ramblings in Ch. 43, had the worse happened, her last thoughts in life would probably have been about seeing her mother again. The entire time Marianne is ill she never mentions Willoughby at all:

Poor Marianne, languid and low from the nature of her malady, and feeling herself universally ill, could no longer hope that to-morrow would find her recovered; and the idea of what to-morrow would have produced, but for this unlucky illness, made every ailment more severe; for on that day they were to have begun their journey home …The little that she said, was all in lamentation of this inevitable delay

Marianne, suddenly awakened by some accidental noise in the house, started hastily up, and with feverish wildness, cried out --
"Is mama coming?"
"Not yet," replied the other, concealing her terror, and assisting Marianne to lie down again; "but she will be here I hope, before it is long. It is a great way, you know, from hence to Barton."
"But she must not go round by London," cried Marianne, in the same hurried manner, "I shall never see her, if she goes by London."

Marianne's ideas were still, at intervals, fixed incoherently on her mother…