This is something I've noticed in my personal story telling studies. It's about Characters and Wants. Simply put all good Characters have wants.
All characters, all of them, or at least the good ones, have a desire, a goal to reach and ambition to achieve. This is especially true for villains, even more so for the good ones.
A character's main desire is part of their characterization, this combined with their personality determines, or at least should, what sort of actions they will take.
Take Nagi from Ultraman Nexus. What did she want? She wanted revenge for her parent's murder. How did she go about doing this? She joined TLT, became a Night Raider and exterminated all Space Beasts with extreme predjudice.
Nagi believed her hatred made her strong and would push her forward and make her strong. When she finally ran into her parents' killer, she rushed headlong into a trap, a mistake that nearly doomed the world.
Let us look at Himeya Jun. He wanted penance for getting Sara killed. This resulted in self loathing and going along with Nexus' demands to stop space beasts and save people with dedication. However, he saw his path, leading to his inevitable downfall as his well deserved punishment. Yet once, he was freed from his guilt, his desire changed. He became devoted to the Light's mission (possibly even resurecting himself by sheer force of will! Yes, Himeya is/was my favourite Ultraman). His attitude changed as his desire changed.
Another example is
Mizuki (I need to finish another series, using Orion is getting old). Her desire was like Nagi's she wanted revenge on her parent's killer. To this end, she hunted down all kaiju and aliens with extreme predjudice. Like Nagi, her actions nearly damned Earth, but after this her desire changed. Instead of simply wanting revenge, she wanted forgiveness from her peers and Ultraman, which ultimately cause her to mellow out.
Orion, is a guy with so much desire. He desired to live up to his dream image of what Ultras where. He desire to escape the shadow of his home world's legacy. Then he desired to protecto the people of Earth because.
A character isn't always going to be ruled by their main goal, sometimes that's not enough or appropriate for the situation. A temporary desire, a goal called about by the situation may be the driving force at any time. A Defense Force Member, may desire to become a general, but when the Earth is attacked, they would put aside that desire, and settle with saving the world.
A kaiju's main goal may be to propagate its species, for that it may need energy, or a nest. So it attacks a city and/or power plant. Then when the army or a Giant Hero comes, their desire turns to defending themselve/ their nest/ meal.
In both cases, their main goal has not changed, but given the situaiton, a temporary goal arises that is of a more immediate importance.
Why it is important
A desire puts a character on the road to character development and/or plot. What is a person going to do, if they don't have a goal? And what is a goal, for some it could be as simple as finding a goal, for their simple boring lives. For most, it's seeing something come to pass, or finding someone, something.
Why someone has said goal, can also be a springboard for exploring their past, and adding history to the story. Main characters, small characters, they should all have goals. People in the same organization could have different goals and desires which may lead to conflict, even if they do share the organization's overall goal(s). This can be true for both bad guys and good guys.
Goals are also what drives the plot, people do things, because they want something or want to achieve something. It is the conflict of goals that gives rise to alot of conflict and drama.
So, next time you decide to create a character, besides deciding their appearance and personalities, maybe you should think about their goals and why they have them.
Granted, only you the author/writer/creator need to directly know what they goals are. Some of the fun of reading fiction, is figuring it out for ourselves.
You could also call a goal a dream. Musashi from Ultraman Cosmos, had a dream of finding peace with kaiju and humans and that set the atmosphere for most of the series. So to can the dream of the main character set the course of the series.