An alien species has been conquering planet after planet around the Milky Way for some time. They detected intelligent life on Earth a while back and now they decided it’s time to add us to their collection. To capture us, they send one of their massive acquisition ships.
They want it to take as little time as possible, so they decide to make an immediate show of power and demand our surrender. To accomplish this, the ship will massively decelerate and stop just before hitting the Earth.
The force provided from this will cause massive natural disasters, and possibly kill a proportion of the Earth's residents, without destroying the planet.
Is it possible to cause such effects by deceleration?
and/or what would the effects actually be?
The ship would be something like a moon-sized battle station (or possibly a giant head…)
The maximum amount of population they’d wish to kill would be roughly 5%.
They can travel faster than light if necessary.
They have the potential to go light speed to 0 in roughly 0.2s, but don’t worry about the how.
I'm not asking about the effects of another moon in orbit, rather just the initial appearance.
Any figures of distance, speed or deceleration would be appreciated!