YOU SAID:

and meeting another colleague there who is apparently unsatisfied at work because I've been neglecting him and he wants to leave

INTO JAPANESE

そこで別の同僚と会うが、彼は私が彼をないがしろにしてきたせいで仕事に不満を抱いており、辞めたいと思っているようだ。

BACK INTO ENGLISH

There I meet another colleague who is unhappy with his job because he feels I have neglected him and wants to quit.

INTO JAPANESE

そこで私は、私が彼をないがしろにしていると感じて仕事に不満を持ち、辞めたいと思っている別の同僚に会いました。

BACK INTO ENGLISH

There I met another colleague who was unhappy with his job and wanted to quit because he felt I was neglecting him.

INTO JAPANESE

そこで私は、自分の仕事に不満を持ち、私が彼を無視していると感じて辞めたいと思っている別の同僚に会いました。

BACK INTO ENGLISH

There I met another colleague who was unhappy with his job and wanted to quit because he felt I was neglecting him.