Screen Capture from Guardians of the Galaxy Vol. 2
Lesson 5: Sympathy for Villains
Calvisi emphasizes the need in creating sympathy for your villains. A good suggestion would be to have their sympathetic traits relate to the theme. You should, of course, first understand your theme. Knowing your theme will help you generate scenes, control your dialogue, and deal with character arcs.
Using Gamora and Ego as examples, both had familial issues: Gamora had to deal with Nebula (her sister), and Ego was an absent father to Peter. The similarities of these characters’ predicaments were not coincidences, as Gunn focused on a family theme for Guardians of the Galaxy Vol. 2. Therefore, he wrote to that theme.
Have your villains relate to the theme and be a little sympathetic—give us a reason to like them. Creating a purely evil villain will only make the character look one-dimensional. Even a bit of charisma will help. All in all, try to get the audience to understand your villains and their motivations.