The Second Council of Lyons: “The souls of those who die in mortal sin or with original sin only, however, immediately descend to hell, yet to be punished with different punishments.”
The Council of Florence: “But the souls of those who depart this life in actual mortal sin, or in original sin alone, go down straightaway to hell to be punished, but with unequal pains.”
Pope Innocent III: “The punishment of original sin is the deprivation of the vision of God, but the punishment of actual sin is the torments of everlasting hell…”
All the souls in Hell have the punishment of deprivation (eternal separation from God). All the souls other than those who died in “original sin alone” also have active torments.
Also, we cannot ignore the teachings of our Lord on this topic. Jesus called Hell unquenchable fire "where ‘their worm does not die, and the fire is not quenched.’ " (Mark 9:48
NABRE)
The “worm of conscience” is the interpretation of Saint Augustine, Saint Bede (in the Golden Catena), and
Saint Aquinas.
Also, the parable of Jesus on Lazarus and the rich man, who died and went to Hell says this:
"And he cried out, ‘Father Abraham, have pity on me. Send Lazarus to dip the tip of his finger in water and cool my tongue, for I am suffering torment in these flames.’ " (Luke 16:24
NABRE)
So the suffering of eternal separation from God is not the only suffering of Hell. Also, it would be unjust if God punished all in Hell with the same degree and type of punishment. So some souls have sinned more, and therefore are punished more.