I think they’d just need to travel slower through space to experience more time relative to the other civilization. Then that civilization could take more that time to develop a civilization-ending laser or whatever.

Then for gravity, the less gravity that civilization experiences the slower time moves for them relative to their competitor.

So I think the goal would be to send star matter to the other civilization so their time slows down relatively speaking.

I’m no expert, though. Happy to take corrections.