Khandavaprastha genocide is the worst thing anyone has ever done in Mahabharata
There are many contenders of the worst thing anyone has ever done in Mahabharata. You may think the title might belong to Duryodhana, Dussashan, Karna, Ashwatthama, or even Yudhishthira.
But the crown actually goes to Krishna and Arjuna.
TV serials show very sanitized version of Khandavaprastha burning. Most of them can't show the reality behind this dark incident. In fact they make the residents of Khandavaprastha evil.
Khandava was the great forest where many tribes, animals, serpents etc resided. Long time ago Agni ate lot of ghee and got fat. Instead of suggesting him cardio, Bramha asked him to burn Khandavaprastha to be healthy again. But that forest was protected by Indra himself, so Bramha asked him to wait until Krishna and Arjuna are born as only they could fight off Indra.
Agni comes as Bramhan and asks them to help him eat (burn) the Khandavaprastha. And that's when they get Gandiva and Sudarshan respectively.
The most painful part as I highlighted is, when Agni started burning the forest, Krishna and Arjuna repeatedly killed the people, animals, tribals who tried to escape.
Actual living beings were scorched alive as you can read and they died yelling, crying.
They were weak, not even fighting or doing anything wrong, but so many lives were made fodder for Agni helped by Arjuna and Krishna. They repeatedly pierced them.
It's truly a genocide.
Indra came of course to defend along with all the gods, and got defeated.
Only 6 beings were left alive. One of them was Mayasur, whom Arjuna "spared", how kind of him!!
There are so many justifications of this event I have seen and never agreed with any one of them
1) It's what supposed to happen and Agni needed to be healthy again
One of the worst justifications of any act is the reliance on natural order. If natural order is supposed to be the criteria, then morality holds no value. Also, intention itself doesn't justify the task. Even if Arjuna and Krishna wanted to "help" Agni, they should have had their moral conscience to differentiate whether the task is morally right or not. Thanos's decision to wipe half of humanity was wrong, despite his intention being right.
Krishna and Arjuna were Nara and Narayana himself. It doesn't matter what Bramha or Agni or Indra says, they should take decisions independently and decisions which actually are morally right. How else they are different from elders of Kuru sabha who think natural order overrides moral responsibilities.
2) Those who got killed attained moksha
Well then the discussion holds no value. If merciless killing by God is justified because the bodies will attain "moksha" or because he is God, then there's no difference between a dictator and him.
3) They were rakshasas
There were mix of tribes, animals, rakshasas who were killed. And moreover, just being born a rakshas shouldn't be a criteria for being murdered for no reason. As long as they were in their own habitat not disturbing anyone, they don't deserve any punishment.