Who is He speaking of here in Peter? If it were all people, hell would be empty since God does all His pleasure.
The Lord is not slow to fulfill his promise as some count slowness, but is patient toward you, NOT WISHING THAT ANY SHOULD PERISH, but that all should reach repentance.
2 Peter 3:9 ESV
Do you know who He is talking about? His sheep. His little ones.
What do you think? If a man has a hundred sheep, and one of them has gone astray, does he not leave the ninety-nine on the mountains and go in search of the one that went astray? And if he finds it, truly, I say to you, he rejoices over it more than over the ninety-nine that never went astray. So it is NOT THE WILL OF MY FATHER who is in heaven THAT ONE OF THESE LITTLE ONES SHOULD PERISH.
Matthew 18:12-14 ESV
Who then are the "little ones"? Little children? No. It is those who are "like children", the believing ones.
“Truly, I say to you, unless you turn and BECOME LIKE CHILDREN, you will never enter the kingdom of heaven. Whoever humbles himself LIKE THIS CHILD is the greatest in the kingdom of heaven. Whoever receives one such child in my name receives me, but whoever causes one of THESE LITTLE ONES WHO BELIEVE IN ME to sin, it would be better for him to have a great millstone fastened around his neck and to be drowned in the depth of the sea."
Matthew 18:3-6 ESV
God will not lose a single one of His sheep, because He wills that none of them shall perish. Period