Kurzgesagt – In a Nutshell posted two videos studying the possible ways a malevolent society can cause problems without even leaving their star system at all.

The Dark Forest solution to the Fermi Paradox (the first strike advantage): https://www.youtube.com/watch?v=xAUJYP8tnRE

How to Win an Interstellar War (without leaving home) https://www.youtube.com/watch?v=tybKnGZRwcU