Question:

Is there anyone who we know is certainly in Hell?

Answer:

The Church makes it a point to pray for everyone in hope that the mercy of God reaches each according to divine will. We trust that those who are trapped in purgatory by the temporal punishments due their sins can get help from the offerings of petition and thanksgiving presented to God for their good. Whilst the Church does not believe a person already in hell can benefit from such prayers and suffrage, she does not however teach that She knows anyone who aside from the Devil and his angels (cf. CCC 392–93), are (or will be at the last day) in hell already. Some like to cite some figures like Judas, Herod etc. However, we can never know their fate since the mercy of God is very mysterious.
We are definitely going to be surprised when we get there. Ours is to pray for all, and not to condemn anyone to hell with our mouths, judgement belongs only to God.

We can therefore hope in the glory of heaven promised by God to those who love him and do his will.92 In every circumstance, each one of us should hope, with the grace of God, to persevere "to the end"93 and to obtain the joy of heaven, as God's eternal reward for the good works accomplished with the grace of Christ. In hope, the Church prays for "all men to be saved."94 She longs to be united with Christ, her Bridegroom, in the glory of heaven:
Hope, O my soul, hope. You know neither the day nor the hour. Watch carefully, for everything passes quickly, even though your impatience makes doubtful what is certain, and turns a very short time into a long one. Dream that the more you struggle, the more you prove the love that you bear your God, and the more you will rejoice one day with your Beloved, in a happiness and rapture that can never end. CCC 1821