Davies
Legend
It's worth noting that Vader didn't give the order there. That was all on Tarkin. Both the radio play and the novelization portray Vader as slightly uncertain whether doing this is a "good" idea (and, in the aftermath, a bit amused that it failed to get the information they wanted.) I don't offer this as exculpation, as the slaughter of the students and torturing Leia, and later Han and possibly Chewie, are sufficiently terrible in and of themselves. But the decision to commit genocide against Alderaan was not his.Now, after Vader blows up a planet? Ok, all bets are off.