Esteban Trueba is the only character to survive the course of the entire novel, so as you can imagine, he's a pretty big deal. Because Esteban Trueba lives such a long time, he's the character we see change the most. This leads some to consider him the hero of the novel. (See if you agree with our assessment of who the protagonist is in our discussion of "Character Roles.")
From a hardworking little boy with wounded pride, we see Esteban grow to be the lord and master of his domain, wealthy beyond his wildest dreams and absolutely certain of the correctness of his convictions. Year after increasingly miserable year, Esteban Trueba continues to get what he thinks he wants while never managing to actually be happy. This probably has something to do with the fact that he drives away all of his family members and spews a lot of ill will that makes most people hate him. Finally, and somewhat miraculously, Esteban sees the error of his ways, makes peace with his family, and dies in bed with a smile on his face.
Esteban Trueba's character provides a balance to all the strong feminine characters in this novel. His masculinity and conservative politics are the yang to Clara and Alba's yin. And while he makes a lot of bad decisions, the fact that many of the passages are written from his perspective allows us to get inside his head and at least understand why he makes them. So, while we might look with horror on his acts of violence against family members and tenants, we come to understand his rage as a product of the humiliation he suffered during his miserable childhood. While we may not go so far as to sympathize with the misguided old man, we do feel a little bit sorry for him. And when he loses his wife and when his son is murdered thanks to his own misguided political tampering, we get why Alba can simultaneously blame her grandfather and want to run up and hug him.