John Fox has created his "Gigantic List of Character Descriptions" with plenty of concrete examples from literature: https://thejohnfox.com/2016/06/character-description/

Even if Sci-fi isn't your genre, you can still glean helpful information in this article by Charlie Jane Anders titled "10 Tips and Tricks for Creating Memorable Characters."

gizmodo.com

Science fiction and fantasy are built on cool ideas and fascinating worlds — but those things are only as good as the people who live around and inside them. How do you create compelling fictional characters? It's a huge challenge. But here are some tips that might make it easier.

For more writing advice via Gizmodo, a design, technology, science and sci-fi website, click here: https://gizmodo.com/tag/writing-advice