[tzs]

You could also do it by arranging for Earth to collide with other bodies whose angular momentum vector points opposite Earth's.

If would take a lot of time but this could actually be done without requiring a huge amount of energy. Find bodies in elongated orbits that bring them from the outer solar system to near Earth's orbit. Send something out to them when they are still far enough away that it only takes a nudge to alter their orbit into one that will hit Earth and give them an appropriate nudge.

To get to the targets without having to use a lot of energy use unstable orbits around Lagrange points [1].

[1] https://en.wikipedia.org/wiki/Interplanetary_Transport_Netwo...