Oscar Wilde's The Picture of Dorian Gray is a clear representative of the Gothic genre. In this genre, the concept of the "doomed self", or the inevitability of fate, is ever-present. The basic tenet is that it is the character's own "flawed constitution" that will bring upon the character every negative force of nature and the supernatural. For this reason, it is Dorian (and only Dorian) who is to blame for his end.
To the untrained Wilde reader, Lord Henry would seem to be the obvious culprit of Dorian's demise. After all, it is Lord Henry who seems to instill in Dorian the ideas of hedonism and debauchery in which Dorian will engage to the fullest.
However, we know that Lord Henry is merely a talker. Nowhere in the story could we be able to point out any wrongdoing on Lord Henry's part except maybe for his openly-expressed disdain for his wife Victoria. Aside from that, what we have in Lord Henry is essentially the author's mouthpiece; his role in the novel is to preach the hedonist manifesto, without actually performing any of it.
Dorian, however, is a different story. When he hears the axioms and ideas that Lord Henry speaks of, Dorian automatically seems to "activate" secret lusts and passions that were laying dormant within his soul. Lord Henry does not corrupt Dorian; actually, anybody who would have preached Lord Henry's same words would have had a similar effect.
Moreover, when we look at chapters 10 and 11, we find Dorian becoming obsessed with "a book" that Lord Henry gives him about a man much like himself whose doomed fate also leads his hedonism to chaos. The content of the book, and the similarity of the character to Dorian draws Dorian's attention because he knows that he (Dorian) is somewhat different from everybody else.
FOR YEARS DORIAN Gray could not free himself from the influence of this book; or perhaps it would be more accurate to say that he never sought to free himself from it.
[...]The hero, the wonderful young Parisian, in whom the romantic and the scientific temperament were so strangely blended, became to him a kind of prefiguring type of himself. And, indeed, the whole book seemed to him to contain the story of his own life, written before he had lived it.
Wilde scholars know that "the book" that Dorian is enchanted with is Huyssman's A Rebours, which is the same book that essentially brought out Wilde's own tastes towards homosexuality and hedonism. Yet, all that this tells us is that nobody but Dorian's own tendencies are responsible for his choices and therefore, for his end.
Concisely, Dorian comes out as a "doomed antihero" whose fate is sealed from the beginning, and whose naturally evil flaws lead him to his own, chaotic destiny.