What is your MC’s shadow side?
When creating characters, even the protagonist, an easy way to give them realistic flaws is to ask what their good aspects look like when taken too far.
Novels are about disasters of one kind or another, from nearly hooking up with the wrong person to surviving the apocalypse (or both at once if you like.) You can make your main character an agent in their own disaster by taking their good aspects to a harmful extreme.
Good intentions with bad outcomes have more plot juice than a character simply choosing to do the wrong thing. The scariest villains are the ones who are convinced that their cause is justified in the name of some greater good.
For example, my new character Owen is: EMPATHIC, DILIGENT, EXTROVERTED
The shadow/extreme of this is that he is: TOO SENSITIVE TO CRITICISM; PRONE TO OVERWORK & OBSESSION; UNABLE TO RECOGNIZE OTHER PEOPLE’S LIMITATIONS.
He’s not a bad person. When he does bad things, it's because his positive traits have been taken to an extreme. He ends up doing wrong because of his good intentions.
We don’t think nearly enough about the negative outcomes that can be caused by positive intentions, in fiction, and in life.
It's in those blind spots that most of the plot happens.