Hypervelocity Relativistic Bombardment

The so called Hypervelocity Relativistic Bombardment is a logical expansion of common Relativistic Bombardment, employed when someone is ready to go for a great lengths to make a planet (or, theoretically, a megastructure) cease to exist.
HRB uses the same principle as Subspace Drive, a cutting edge evolution of Hyperspace Drive for warships. It allows a ship to 'slip' on the surface of the Hyperspace, essentially achieving an FTL speed in Reality by being partially phased out of said Reality.
This technology is used to accelerate the round to FTL speed, allowing it to circumvent the limits of Einstein physics and gather the amount of kinetic energy that's normally impossible. In the end, if there was a material strong enough to survive that, a HRB round could shoot THROUGH planets. Since it is not possible for now (neutronium and quark matter are suspected of being resilient enough), the round is destroyed the moment it hits the target, still carrying enough kinetic energy to sterilize and shatter the planet. It was used merely few times in history, against threats like pre-Virus automata that couldn't be contained in conventional way.