In addition, the toxic undermined the authority expressed themselves in a self-authoritarian manner, and showed insensitivity by isolating themselves from their peers and not caring about the issues a

In addition, the toxic undermined the authority expressed themselves in a self-authoritarian manner, and showed insensitivity by isolating themselves from their peers and not caring about the issues and welfare of the employees.

I’m told I need a comment after the word expressed and before the word themselves?