> it’s conjectured that the colonists already at your destination won’t appreciate you boiling the atmosphere when you hit them with blue shifted radiation.
There's a general principle known as Jon's Law (not sure where the name comes from) that any powerful space drive is by definition a weapon of mass destruction.
You see this in The Expanse when incredibly powerful fusion torchship rockets (a major part of the Expanse 'verse) are attached to asteroids and these are used to kinetically bombard inner planets. The results are far worse than a nuclear attack, from kinetic energy alone.
Anything capable of traveling close to the speed of light would be "death star" level planet killer. We're talking smashing through the crust and boiling off the atmosphere or if it were massive maybe even fragmenting the planet. Obviously anything even wilder like an Alcubierre Drive would be likewise. Anything capable of going to the stars within a human lifetime could annihilate worlds.
Even present-day chemical rockets could be pretty destructive. Get something massive that won't burn up (like a rod of tungsten) up to interplanetary velocities and you can approach the yield of a small tactical nuke from just kinetic energy. This has been studied at least on paper by militaries. I think the phrase "rods from God" was used by DARPA at one point for the rod of tungsten idea.
This is glossed over in the vast majority of space sci-fi. Nobody even asks in Star Trek what happens if you point the Enterprise at a planet and say "warp 9, engage!" I'm guessing it would go poorly for the Enterprise but even worse for the planet.