One of the things He can do is wipe out humanity. He was grieved with us in Genesis before the flood. But He did not erase us from the earth. He CAN do it. He did not. He preserved a remnant, Noah and his family. He always preserved a remnant of His people the Jews.
It is promised, "A remnant will return, the remnant of Jacob, to the mighty God." (Isaiah 10:21). There was a remnant returning from the Babylonian captivity. A remnant of 7000 was preserved when Elijah killed the false prophets of Baal when he thought he was the only one left.
But I want to bring another thought to your mind. Christians are a remnant too. We know the multitudes which are His bride will be singing praises to Him after the Rapture. We read passages like this "And I heard every creature in heaven and on earth and under the earth and in the sea, and all that is in them, saying, "To him who sits on the throne and to the Lamb be blessing and honor and glory and might forever and ever!" (Rev 5:13) and think, 'Wow!' Lots of Christians!' While it is so in heaven, the number on earth is not as large as we think.
The odds are not good for making into Christianity. We know that the road is narrow and FEW FIND IT. (Mt 7:14). The road to destruction is broad and MANY FOLLOW IT. (Mt 7:13). We know that Jesus said,
"Not everyone who says to me, ‘Lord, Lord,’ will enter the kingdom of heaven, but the one who does the will of my Father who is in heaven. On that day many will say to me, ‘Lord, Lord, did we not prophesy in your name, and cast out demons in your name, and do many mighty works in your name?’ And then will I declare to them, ‘I never knew you; depart from me, you workers of lawlessness.’" (Matthew 7:21-23)
Are you getting the picture? Many/Few. It is a theme. How many righteous did Abraham ask the LORD to find in Sodom? "He answered, “For the sake of ten, I will not destroy it.” (Gen 18:32b). But it ended up there were less than ten. So four cities were destroyed that day: Sodom, Gomorrah, Admah, Zeboiim. And of the four that were found to be righteous, Lot, Mrs Lot, and the two daughters, one of the four was revealed to be a false righteous and was turned into a pillar of salt.
There seems to be a lot of us but we can't accept just any old profession of faith. Many faithless have grown up among us, the Judas' and Demas' among us are alive and well.
Christians on earth are a remnant. I say 'on earth' because if we add the multitudes of aborted babies, infant and child deaths throughout the ages, this swells it be number in heaven considerably! But on earth, perhaps not so many true Christians.
Examine yourselves, to see whether you are in the faith. Test yourselves. Or do you not realize this about yourselves, that Jesus Christ is in you?—unless indeed you fail to meet the test! (2 Cor 13:5)
Here is an essay that helps you test yourself and see if you bear the distinguishing marks of being a Christian.
Of those that fail to meet the test, there will be weeping and gnashing of teeth.
The Son of Man will send his angels, and they will gather out of his kingdom all causes of sin and all law-breakers, and throw them into the fiery furnace. In that place there will be weeping and gnashing of teeth. Then the righteous will shine like the sun in the kingdom of their Father. He who has ears, let him hear. (Mt 13:41-43)
I want to sing with you in heaven, and I do not want to see you thrown into outer darkness, weeping and gnashing your teeth, screaming, LORD, LORD did I not do many mighty works in your name? And He will say to you, I never knew you, depart from me you evildoers!
Are you in the remnant??? Praise Jesus if you are. Let His light of glory shine in you and through you. Let us give it all back to Him in thanks for salvation which He delivers through grace plus nothing. No works of ours, mighty or mild, will earn us heaven. But believe on the Son whom the Father sent, and ye shall be saved.