It may even be worse than aloneness.
Imagine a marriage: two people in love. Then bleed every last drop of love out of it. Imagine two people living together and despising each other more and more every day. Forever.
Hell is a whole country like that.
I've heard this often stated. But what does the Bible say?
The same shall drink of the wine of the wrath of God, which is poured out without mixture into the cup of his indignation; and he shall be tormented with fire and brimstone in the presence of the holy angels and in the presence of the Lamb: (Revelation 14:10)
God (Jesus Christ, the Lamb) is right there in hell. And so are his angels. It is not aloneness--that is a false doctrine.
We also know from 2 Thess 1:9 that everlasting destruction will emanate from his presence and from the glory of his power. (All the modern versions translate [apo] "from" incorrectly as "separation from"--they add words. That would make the Bible contradict itself. The KJV (and possibly NKJV?!) gets it right: His presence is the source of the everlasting destruction.)
Let's be honest. Endless torment has to be the most horrifying prospect, not being "alone." And this is what awaits those who try to earn heaven by their good works and not trusting in the gospel to save them.