Seven-shot weapon, that Starkiller
[*spoiler warning*]
So Starkiller is basically able to destroy just seven targets (six Republic worlds) and D'Qar in the Ileenium system before completely draining the star. After draining its star, it's completely useless and needs to be evacuated. It cannot move, there is no mention of any engines on that thing, and not enough energy left to move it, anyway.
Don't even get me started on how the beams are visible all over the galaxy at the same time. It's not about visibility itself, since these are not lasers, but if they move in hyperspace, they shouldn't be visible at all. And certainly the destruction of the six Republic worlds should not be visible from anywhere but just that one system (unless the galaxy is really tiny, in which case you wonder why they need hyperdrives in the first place).