Alec is deceitful, manipulative and a bully, and, like all bullies, he is easily manipulated himself by another bully or officious person. This is why Angel's father was able to coerce Alec into a radical change of lfe and also why the change could not hold up when presented with external facts or attractive alternatives.
"I have arranged to preach, and I shall not be there—by reason of my burning desire to see a woman whom I once despised!—No, by my word and truth, I never despised you; if I had I should not love you now!"
D'Urberville is deceitful and manipulative from the first, and it is these traits of his that lead Tess to her doom--she has to be tricked by vile means to succumb to Alec and his traits make him an expert at trickery. It is through trickery that he also begins to approach Tess in the hope that he will win her over to reuniting with him:
D'Urberville in anger retreated from her to the hedge, where he pulled off the long smockfrock which had disguised him; and rolling it up and pushing it into the couch-fire, went away.
Nonetheless, there is a sincere and earnest side of Alec that is surprising and often leaves others in doubt of his true personality. when Tess's father has died, Alec offers Tess a home for herself, her mother and the children. Alec seems to be acting and speaking with perfect sincerity. He generously promises to provide all they need and to expect them the next day, since the "lifer" lease of the cottage ended with her father's death. In the midst of this compassionate sincerity, he reaches his hand in the window to console Tess whereupon she crashes the window casing down upon his hand.
"I owe you something for the past, you know," he resumed. "And you cured me, too, of that craze; so I am glad— ... I am glad of this opportunity of repaying you a little. To-morrow I shall expect to hear your mother's goods unloading… Give me your hand on it now—dear, beautiful Tess!"
Another important trait of Alec's is his anger. He easily dissolves into virulent anger that holds resentment and revenge and refuses to let go. Had it not been for this revenge tinged anger, his and Tess's stories may have had different endings. When Angel finally does come home and finally does seek out his wife, both of them wasted and wan--he wasted in both exterior appearance and interior state, she wasted on the interior though now blooming on the exterior--it is Alec's angry reaction to Tess's sorrow and torment that leads to his violent end.
There were more and sharper words from the man; then a sudden rustle; she had sprung to her feet. ... Mrs Brooks had strange qualms of misgiving. ... she fancied that it was a blood stain.
Clearly the villain of the novel, Alec d'Uberville escapes being a stock character when he finds religion, for his conversion provides him some depth as a personage in narrative.
- Victorian Stock Character
Despite his roundness of character later in the narrative, however, Alec certainly resembles in physical appearance the Victorian villain with the black moustache and what Victorians perceived as an ominous dark complexion and eyes. His physical description is in Chapter V:
He had an almost swarthy complexion, with full lips, badly moulded, though red and smooth, above which was a well-groomed black moustache with curled points, though his age could not be more than three-or four-and-twenty. Despite the touches of barbarism in his contours, there was a singular force in the gentleman's face, and in his bold rolling eye.
- An Opportunist/Symbol of the emerging merchant culture during the Industrial Revolution
One of Hardy's themes is the alteration of his beloved English countryside fictionalized as Wessex, representative of southwest and south central England. With Tess as symbolic of the bucolic in its unaltered beauty that is threatened by the intrusion of the machinery of the Industrial Revolution, Alec d'Uberville represents the mercantile class that aspires to the level of the aristocracy. While Tess's mother believes that the d'Ubervilles are aristocrats, in truth Alec's father was a successful merchant who attached the name "Stoke" to his family name in order to give it the appearance of respectability. (This is why Alec asks Tess if she is a "Stoke" after she introduces herself as a relative.)
The prestige of Alec d'Uberville, therefore, is illusory, but he uses it to overpower others such as the Queen who wants to fight Tess and to control Tess. This usurpation of power over the working class is symbolic of the oppression of the emerging merchant class of England and the displacement of the agrarian people effected by the new technology.
As a member of this pedatory class, Alec seizes the opportunity to offer the cottage on his estate to the Durbeyfields when Tess's father dies. In Chapter 48, he tells Tess,
"If I cannot legitimize our former relations, at least I can assist you....I have enough... to put you out of anxiety, both for yourself and your parents and sisters, I can make them comfortable if you will only show confidence in me."
- A character with the trait of metanoia ["change in one's way of life resulting from penitence or spiritual conversion"]
Ironically, Alec undergoes a religious transformation at the hands of Angel Clare. As mentioned, it is this conversion which gives Alec more depth. However, it is also this conversion which lends his character amorality as he so quickly abandons any religious faith when he meets Tess by chance, proving that the innate seducer/predator nature of Alec has been merely sublimated to religious zeal. He explains to Tess in Chapter 47,
" If there's nobody to say, 'Do this, and it will be a good thing for you after you are dead; do that, and it will be a bad thing for you,",,,, Hang it, I am not going to feel responsible for my deeds and passions..."
- A predator
In Chapter 11 as Tess rides with Alec is "inexorable" and later rapes her as she sleeps.
...upon this beautiful feminine tissue, ...there should have been traced such a coarse patterna as it was doomed to receive.
In Chapter 48, he exploits the Durbeyville poverty to subjugate her again.