Mr.__ (or Albert as he is occasionally called) may be a jerk for most of the book, but at least he changes. Mr.__ is one of the only male characters in this novel capable of reflection and personal growth. By the end of the book, he and Celie are actually pretty good friends.
The impetus for his growth is Celie leaving him. When Celie joins Shug in Memphis, he has to face the facts: His wife left him for his lover, and his lover chose his wife over him. He’s a failure. But instead of doing what we expect—that is, become even meaner— Mr.__ realizes that "meanness is killing" him. He tries to make up for the wrongs he has committed against Celie, namely giving her all of Nettie’s letters that he had been hiding. Doing the right thing transforms Mr.__ into the kind of person Celie actually wants to be around.
Interestingly, part of Mr.__’s transformation involves taking on characteristics that are classically seen as "feminine." Sexist for the majority of the book, Mr.__ saw women as stupid, in need of beatings and constant direction from men, and useful only as sexual objects and laborers. Mr.__ also taught these values to his son, Harpo, sneering at his son for not beating Sofia and asserting his dominance. However, as Mr.__ becomes nicer, he finds interest in traditionally feminine activities. As it turns out, Mr.__ enjoys cooking. He keeps a clean house after Celie leaves. In fact, he even enjoys sitting on the porch and sewing with Celie.
Many people have criticized Alice Walker, claiming that she represents all males in an extremely negative light. However, if you want to make that claim, you have to contend with Mr.__/Albert. He clearly develops into a really decent guy.