What made Macbeth evil and selfish?
Primarily, it is his ambition and pride that makes Macbeth so evil and selfish. Before he commits the murder of Duncan, he lists all of the reasons he has not to kill the man who is his king, guest, kinsman, and friend. He has only one reason to go through with it, and that is his "Vaulting ambition" (1.7.27). He wants to be king. When the Weird Sisters told him that he would become Thane of Cawdor, and then he did, it made him believe that they were telling the truth in all things. Therefore, he began to dream of becoming the king since that was the other "prophecy" they gave him. His single-minded desire for the throne, and then his desire to retain it, compels him to consider only his best interest and no one else's, and so he becomes quite selfish.
Further, his pride helps to turn him into an evil man. When he learns that Macduff has escaped him and fled to the English court to meet with Malcolm, the real heir to the throne, he feels like it is necessary to wound Macduff in some bigger and worse way. Thus, he decides to "Seize upon Fife, give to th' edge o' th' sword / [Macduff's] wife, his babes, and all unfortunate souls / That trace him in his line" (4.1.157-159). His pride urges him to wound where he feels he has been wounded, and so he commits his most brutal and evil murders yet: those of an innocent woman and her children.