Pantcelot and mael are definitely not in similar situations. Mael had no choice in anything that happened to him, it was a revenge imposed on him by Gowther specifically to make him suffer (and bring the war to a halt for some time).
It’s funny how you try to ignore just how atrocious Mael’s actions were, even before he became Estarossa, simply to push your own agenda and fuel your hatred.
If you’re going to hold Lancelot accountable for the actions of "Chaos Lancelot" even though he was forced into that state as a consequence of his own choices, then I don’t see how you can absolve Mael of responsibility for his time as Estarossa, which was also the direct result of Mael’s own actions and decisions.
Mael wasn’t just some random victim chosen by Gowther.
He was the biggest killer of the first Holy War, earning the title "Angel of Death", He slaughtered innocent demon civilians who were begging and weeping before him, solely because of their race, one of this group included Glariza, Gowther’s beloved, and that why he chose him.
The only reason the 1st holy war Mael didn’t wipe out the entire demon race is that he simply wasn’t powerful enough to do so.
And what has Lancelot actually done so far, by comparison?
In Camelot? He evacuated all the inhabitants beforehand, the only ones left were a band of mercenary knights, with whom they was at war, and Jericho, who chose for herself to die alongside Fakecelot.
In the Demon Realm? He barely killed a few demons before the Induras and Zeldris intervened.
His total kill count so far consists of :
a small band of mercenaries, Jericho (who chose her own fate), two Indura, Zeldris, and a few of random demons.
Mael used to kill more than that in a single day during the Holy War.