Fear.
It drives all of the protagonists.
It is their motivation for everything they do.
Parrot
Parrot is afraid of losing people. The fear that drives Parrot is the fear for others. Fear for their safety. Not his own. (Never his own... That's his fatal flaw. The one thing all his friends screamed at him about. You need to be more careful! You need to think of yourself sometimes!) He's so afraid of others, so afraid of losing others. That is his motivation for everything he does.
Wemmbu
Wemmbu is afraid of being perceived as weak. Afraid to go back to that time where he was weak. Where he was helpless. He's driven by his fear of going back to a time where he wasn't feared. He must be feared! Because if he's not feared then they'll just walk all over him. They'll tie him up. Stab him in the back. Squish him beneath their feet. He will always choose to be feared rather than to be loved. At least he has power if he's feared. That is his motivation for everything he does.
Flame
Flame is afraid to care. He is the opposite of Parrot. If he's afraid for other people that makes him weak. That leaves him open for attack. He's the opposite of Parrot and the mirror of Wemmbu. He's not afraid to be perceived as weak, because he never has been and never will. But he's terrified of caring. Terrified of needing to protect someone. Because he only knows how to protect himself. He's afraid to be perceived as weak for caring. He is the great and terrible Immortal Demon. And demons don't care for people So he shuts them out. Stabs them in the back. It's all he knows how to do. It's the only way he knows how to keep himself safe. He's afraid to care because it will only hold him back. There's nothing he can do with someone else's help that he can't do alone. That is his motivation for everything he does.
And finally...
Spoke
It took me a while to figure out what drove Spoke's character. But it finally clicked earlier today (you can go read the full breakdown on my page. Should be just under this one)
Spoke is terrified of what he sees inside himself. Terrified of what he could become. Jamato saw it in the early days. The terrible darkness inside him. So he left in an attempt to quell it. To ensure he did not teach Spoke something deadly. (And ended up only fanning the flame) Spoke is terrified of becoming the monster that deep down, he knows he is. So when Ash called him out on it, told him he'd become exactly the same as Ash, Spoke knew he was right. His fear of becoming something terrible drives every single decision he makes. Yet in an attempt to avoid becoming that person, he just seals his fate. He's so afraid of becoming a monster that his actions performed in fear only make him more into one.thats why Rose's death haunts him so much. Because it proved Ash and Jamato right. Because it proved that little voice in the back of his head right. Leo saw it in him. Zam saw it in him. Lettuce won't even send his own lawmen after him because that is a fate too cruel, even for criminals and nobodies. Spoke's fear is becoming a monster. And how everything he does only proves that he is one. That is his motivation for everything he does