At what point does a soul go so low that God must take form to personally end them?

i’ve been thinking a lot about the evils and goods in this world. Though i know those who do evil never truly find inner peace if they never change their ways, and that their actions will always have consequences in Karma, i still think about Times were these evils could no longer be allowed to stay and have to be personally taken out by God. For example, When Durga fought Raktabija and entered a Rage and become our mother, Maa Kali, or Vishnu when he took form as Narishma, both in some stories had to be pacified by Shiva. when does one’s sins become so bad they have to have their lives taken by God personally? or is it simply because nothing mortal could have stopped these demons due to their abstract immorality’s? is that part of the reason why we never “see” God until Kaliki in years to come? or is it just fate for Bhagwan Vishnu to come at fixed points in time? regardless, i just hoped to talk about this with more educated and wiser people