[Agemegos]

Range.

You need a large objective to focus a beam at great distance, which in GURPS Spaceships means a powerful weapon, which requires a large ship. So build go with TL 10 or TL11 and build SM +12 warships with 100 GJ spinal UV or X-ray lasers. Fit each one out with a tertiary battery of thirty 1GJ very-rapid-fire UV lasers for RoF 3000 missile defence.

Then stand off at 100,000 miles and plink with the Big Gun. Any warhead or fire platform will cop hell while closing.