2 Timothy 2:12. Was Paul not saved when he wrote it? Would he be saved if Christ was to deny him?
Romans 8 14 For all who are led by the Spirit of God are sons of God. 15 For you did not receive the spirit of slavery to fall back into fear, but you have received the Spirit of adoption as sons, by whom we cry, “Abba! Father!” 16 The Spirit himself bears witness with our spirit that we are children of God, 17 and if children, then heirs—heirs of God and fellow heirs with Christ, provided we suffer with him in order that we may also be glorified with him.
John 17 22 The glory that you have given me I have given to them, that they may be one even as we are one, 23 I in them and you in me, that they may become perfectly one, so that the world may know that you sent me and loved them even as you loved me.
Hell is not going to be full children of God who have been adopted into God's family, are heirs of God and fellow heirs with Christ, that the Father loves the same way like His Son. Hell is not going to be full of members of Christ body.
Now that we established that Salvation cannot be lost, because Christ paid the debt in full for every true believer, let's look at the above verse you posted 'if we deny Him, He will deny us'
There are only two possibilities of people who profess Christ, the real and the false. If we endure, we’re the real and we’ll reign. If we deny, he will deny us. You remember what Jesus said? “If you confess me before men, I’ll confess you before the angels of God or before my Father in heaven. If you deny me before me, I’ll deny you.” If ever anyone denies Christ, rejects Christ, all they manifest is that they never had the real faith, because the real faith is an enduring faith, it is the gift of supernatural faith that endures to the end.
2 Timothy 2:13. “If we are faithless, he will remain faithful, for he cannot deny himself.” And he has identified himself with you. He has given you to share in his life. Those who endure are the true believers. Those who do not endure are false professing believers, and the true believers will have temporary struggles with their faith.
And it’s true. There are times when our faith is weak. And do we forget the words of Jesus who said to his own devoted followers, “O you of - ” what? “ - of little faith?” But never outright denial in some final and complete sense.
If you still claim that those who been adopted to God's family, children of God who the Father loves the same way as He loves His Son will end up in hell, then we have nothing to talk about.