Is Butcher of Torfan a monster? Or one who sacrifices thousands of human/alien lives to save/sacrifice the Council? Or one who kills 300,000 Batarians on Aratoht? The series are filled with such acts the final choice doesn't change what you've become after all three games.
Persuading the Catalyst? Please. You broker a peace in the face of a common threat and no one can tell for how long it'll last and what will come out of it. You can bet the galaxy on it, but an AI can't take such a gamble.
Butcher of Torfan? Well, it depends upon how you look at it. I'm pretty sure those being held by the Batarians on Torfan considered her to be the "Liberator of Torfan" and thought those Batarians got what they deserved. A Colonist Shepard would have considered it payback. Who knows? Maybe the sergeant who killed her parents was in command of the Batarians?
Khalisah was the reporter we were supposed to hate, but Emily Wong was the one who called her The Butcher of Torfan. Damned liberal media. That's Batarian propaganda. The Alliance would have spun it to "Liberator of Torfan." But we were so desperate for money at the time that we did her fetch quest. However if we hacked and gave ourselves 999999999 CR we could simply not do her quest.
And really? Warning could not be successful. Science fiction writers have no sense of scale. Even 2 hrs warning to evacuate a planet it would take the communication probably 2 hrs to reach Aratoht. Think, Shepard. Communication travels at the speed of light within systems. Please note that the distance between the worlds are not to scale on these drawings. If they were, the gravitational fields would tear the worlds apart when they passed. If we guesstimate that the first planet is .5 AU and Aratoht is 1 AU then, and each orbit doubles, then the asteroid belt is 16 AU. It would take 2 hrs 5 mins for the communication to reach Aratoht from the asteroid.

And given that the blast from the relay travels at the speed of light, they have 2 - 3 hrs to evacuate the entire planet. This means 1) Authorities believing your warning; 2) then notifiying other colony authorities and getting everyone to shuttles (panic); 3) and getting to the mass relay before the asteroid --- impossible. The train must stay on the rails. End result is that it doesn't matter - The only choice that does matter in this case is if you tell Admiral Hackett: "I'm busy," and not do it. Hackett will send in the 105th marines to do the job.
And another huge plot hole? There is no way that the reapers would have been able to detect the blast before it reached them. It travels at the speed of light.
My guess is that the workers on the asteroid had some kind of weird altar rigged up at the communications tower that used the mass relay for reaper worship where they made direct contact with Harbinger.
But if you're a good person, and you know with certainty that using the crucible would allow you to control the reapers (the damage to the relays was bullsh*t in this ending - the blue wave and explosions were completely unnecessary - only new orders from the boss were needed), then choosing Control was the answer. Only your personal sacrifice was needed to end the war. No one else dies.