I use the word "godlike" because of just the magnitude of the energies and timescales we're dealing with. Drawing analogies with contemporary technology and behaviors really understate the magnitudes we're talking about.

Let's assume these aliens are dealing with just well understood Einsteinian physics. Nothing theoretical like wormholes, or thing. Their weapon of choice, is the same weapon of humans million years ago -- throwing big rocks.

Now, finding the mass of asteroids online is pretty difficult. It seems like most asteroids aren't actually measured, because the distribution of mass is highly skewed towards the Ceres, but two I'll look at are: 10 Hygiea, with 8.32E19 kg and 101955 Bennu (of OSIRIS-REx fame), at 7.329E10 kg.

Now we don't need to blow up the Earth Alderaan style. Instead, we'll aim for a Chicxulub impact, which apparently released something close to 4.2E23 J.

We'll also be pretty conservative about where aliens are, and assume they share our galaxy. This puts them at most around 100,000 light years away (the diameter of the Milky Way).

Let's say that we're accelerating our rock to 1% the speed of light. That means it would take 10 million years to hit your target. To put 10 million years into perspective, that's roughly how long ago chimpanzees and humans diverged. You're literally shooting at a species that probably won't exist, to protect your own species, that also probably won't exist.

Accelerating Bennu to 1% the speed of light would require 3.74E32 J and give an impact energy of 79x of Chicxulub. Hygiea at 1% would require 3.74E32 J be 900 million times the size of Chicxulub (8x the Great Impactor Event that birthed the moon). To put this in perspective, the Sun generates 3.8E26 J per second. You'd need to capture the entire output of the Sun for a day at 100% efficiency to accelerate Hygiea to 0.01c. Bennu takes a modest .0009 seconds of solar output.

10% the speed of light? 3.77E34 joules for Hygiea (9E10x Chicxulub) and 3.32E25 joules for Bennu (8x Chicxulub).

Just for giggles, 90% the speed of light gives 9.68E36 joules (800 years of solar output) to accelerate Hygia (2.3E13 Chicxulub, or 2 million times of the energy released by Great Impactor Event that formed the moon) and 8.52E27 joules (2.25 seconds of solar output) for Bennu (20000x Chicxulub). In this case, we'd be atomizing the planet in around just over 100,000 years.

On the other side, if we yeet these rocks at the speed of Voyager 1 (0.00005c, or 17000 m/s), it would take 2 billion years hit, and we'd get 20,000 Chicxulubs from Hygiea at the cost of 9.36E27 joules (2.5 seconds of solar output), and Bennu wouldn't even come close to Chicxulub, but rather a mere 4000 Tungustas at a cost of 8.25E18 joules.

If we want to cause 1 Chicxulub in 10 million years, we need to fire a mass of 1E11 kg, using 4.5E23 J of energy.

This is of course assuming that we're able to hit this planet without any course corrections. A planet mind you, we probably couldn't even theoretically image given the vast distances, infinitesimal angles, and the paucity of reflected photons that hit our telescopes. But hell, maybe we can develop some massive explosive or something that can last 6 million years to redirect our rock as we get closer to the system. The fact that we have to design an autonomous command and control system to last 10 million years in interstellar space is quite a lift, but let's just assume we get lucky.

Here's a spreadsheet of my work
https://docs.google.com/spreadsheets/d/1_W_mJ1ev1mkvZZMkwVlJ...

References
Wikipedia for masses and diameters
https://www.omnicalculator.com/physics/relativistic-ke
https://www.centauri-dreams.org/2012/04/13/collisions-in-the...