So you've got a star. Main sequence type, more or less middle of its life-cycle, nothing special. Probably has an inhabited planet or two orbiting it. Of course, the Evil (Space!) Empire wants the people on the planet(s) dead. They could just carpet bomb the planet or maybe even blow it up, but instead they decide to go for broke. When a faction or character goes Star-Killing they go about ending a star's life in any of a variety of ways that dooms all life in the system to a Class X-2 Apocalypse How. Examples of Star-Killing include: