You have to be careful treading the fine line between Don't Shoot the Messenger and Shoot the Messenger. Of course if you're reporting to the Big Bad Evil Guy, you kind of have to expect to be arbitrarily disposed of at some point anyway, so perhaps it doesn't matter too much.
Commentary by memnarch (who has not seen the movie)
Oooooookay then, time for a quick exit stage right for General Hux. Snoke doesn't seem like the type to enjoy getting bad news, and Kylo won't hesitate to kill the messenger if Snoke does get angry about the news and wants Hux dead. I'm betting Hux isn't going to live through the end of the movie either way since he has a rather forgettable character design. Combed hair, plain black suit, no rank pin, sometimes a hat; if the hair color isn't mentioned, one could think this unfortunate is the one being described instead.
Obviously now, this can't be close to the movie plot. While I was mostly certain Episode VII here wouldn't bother referencing some dude that died halfway through a different movie and that he's not the weapon designer in the first place, the PowerPoint presentation part definitely tosses that idea out. With how much energy is actually needed to explode a planet (versus just melting it for example), it's probably more likely that it's just a "cool/unexplained super tech" type plot hole. Assuming it is a plot hole anyway, I would say it's only a lot more obvious here due to the movie going fancier/bigger/better on almost everything else; this one thing is just a miss for me without the dramatic CGI sequence.
Snoke: What are you saying?
General Hux: Galen Erso has pulled another of his stunts. The Cataclysm Beam doesn’t work as we thought.
Snoke: Did it not destroy Chandrila?
General Hux: We’ve decrypted some of his notes. It seems he designed the weapon to impress Imperial officials.
General Hux: They wanted to see a nice explosion. Erso realised if there were a significant time delay, it’d be his head on a platter.
General Hux: Rather than go to the bother of explaining the physics, he thought it would be easier to just make the Beam travel backwards in time.
General Hux: If it takes minus 10 years to reach a target, light from the explosion reaches the viewer 10 years later, just after the button was pressed.
General Hux: Our Beam travelled 50 light years, moving back in time. Fifty years ago, Hosnian was in the direct line of sight to Chandrila. So the Hosnian catastrophe of 50 years ago was caused by, well... us.
General Hux: It’s all explained in excruciating detail in a PowerPoint presentation.
Snoke: This is absolutely unforgivable!!