Hell is an interesting subject. "Outer Darkness" is also spoken of as a destination. Who goes to which? Don't know. However, God knows and is just. Would it be unjust for some people to go to a hot hell? Well they have to go somewhere to await trial at the Great White Throne. God is good, so to reject him is to choose the absence of all that can be possibly be considered as "good". God respects choices.
From a standpoint of being just ...lots of people have burned others and so a like punishment wouldn't be out of the question. Hitler burned millions in the ovens, arsonists have killed huge numbers of people, burning them alive. So, there are crimes that would qualify in a eye for an eye sort of way.
One thing that you can be sure of is that most, whatever their crime, would consider most any form of punishment as inappropriate. But it is not the guilty's opinion (who excuse themselves) that matters. However "reasonable" their position, their exists a perfect judge.
Furthermore, today in "civilized" society we burn little kids all the time. The victims are the most vulnerable and innocent among us....made in the image of God, babies.
"A needle is inserted through the mother’s abdomen and amniotic fluid is withdrawn and replaced with a solution of concentrated salt. The baby breathes in, swallowing the salt, and is poisoned. The chemical solution also causes painful burning and deterioration of the baby’s skin. 30 to 35 hours later a badly burned and shrived baby is born."
This hospital was caught burning murdered baby bodies to help heat their facility. Just hideous.
Again, it is not yours or mine opinion that matters on such things. We are the guilty party so our opinion is biased. Further, you might think that burning babies is someone's right. Others might think that hell is too good for perpetrators of such heinous acts. All irrelevant. God's sense of justice is the only one that matters.
God emplors us to first seek peace with him through Jesus' work on the cross and to also seek kindness, goodness and especially grace and mercy. This is the heart and essence of God.
God encourages us to not seek justice in the way you are doing in attempting to judge God, because we are 100% likely to end up getting what we ask for - Justice.
And, whatever that justice is we are almost certainly going to be opposed to it. The Gates of Hell are all locked from the inside Cofty. It is chosen just as life is chosen.