It never fails. As soon as some wicked person, some person who is famous for committing many grave sins, dies — apparently unrepentant — there are calls by Catholic commentators to pray for their souls.
There is, at the very least, a problem with emphasis here. Every time a person who lived a very sinful life dies, without any indication of repentance, some Catholics call for prayers for their souls. There is no emphasis on prayers for their repentance before they die. There is little emphasis on on prayer for deceased priests and religious, for deceased family members, for deceased fellow Catholics. But one can find plenty of blog posts on praying for the ‘repose’ of the souls of the unrepentant wicked.
As for me, even in the very unlikely event that Jack Kevorkian repented thoroughly and sincerely just before death, and was sent to Purgatory, I would not pray for his suffering there to be lessened. Instead, my prayer would be that, as Christ said, he not go forth from there, until he has repaid the last quarter (Mt 5:26). For he did much harm to many souls in this life, and so he deserves to be punished in the next life (most probably in Hell).
God’s Mercy is infinite, but those who refuse to accept that Mercy by repenting from grave sin will not receive it. And the infinite Mercy of God is also infinitely Just; therefore, there is punishment for sin.
Finally, it is the infallible teaching of the Magisterium that anyone who dies unrepentant from actual mortal sin will certainly be sent by God to Hell forever. They cannot be saved in some mysterious way known only to God.