In my opinion, great software engineers are not afraid.
They are not afraid of technical(or any kind of) challenges, as they derive joy in overcoming them.
They are not afraid to admit their mistakes(or that they don't know something), as they see it as an opportunity to learn and grow.
They are not afraid to reach out or communicate with others, because they know that no man is an island.
Also, great software engineers are caring.
They care about their work, the people they work with, and the users of their work.
P.S: I am not a great software engineer. I aspire to be one