The NASB reads - Pursue peace with all men, and the sanctification without which no one will see the Lord. (Hebrews 12:14). Without justification, there is no sanctification. Our ongoing sanctification has no bearing on our justification. That is, even if we don't reach entire sanctification/sinless perfection in this lifetime (which we won't) we are still justified by faith in Christ.
How many people who are justified will end up being glorified? Romans 8:30 - Moreover whom He predestined, these He also called; whom He called, these He also justified; and whom He justified, these He also glorified. ALL of them.
Those who are truly born of God have received a new nature, a divine nature, and they have new and different appetites and desires. They have been transformed from pigs and dogs into sheep. The change is more than just cosmetic, as in 2 Peter 2:20. *These cleaned up on the outside dogs and pigs were never sheep.
*Compare 2 Peter 1:4 - "partakers of the divine nature," having escaped the corruption - Strongs #5356 that is in the world through lust with 2 Peter 2:20 - with they escaped the pollutions - Strongs #3356 (different Greek word) of the world through the knowledge of the Lord and Saviour Jesus Christ, yet they are again entangled therein, and overcome. *Notice that 2 Peter 2:20 did not mention them being "partakers of the divine nature."
Corruption (Strongs #5356) (to shrivel or wither, spoil , ruin , deprave, corrupt , defile, to destroy by means of corrupting, to spoil as does milk). Corruption - describes decomposition or rotting of an organism and the accompanying stench. The utter depravity of the fallen flesh and the resultant moral decomposition of the world opposed to God is driven by it sinful lusts or evil desires. Internal corruption.
Pollutions/Defilements (Strongs #3393) ("pollutions", "filthy things", "contaminations", "world's filth") describes the state of being tainted or stained by evil and refers to impurity, impure, tainted, defilement, foulness or pollution.
Pollutions/Defilement refers to what is on the outside (2 Peter 2:20). But genuine believers have escaped the "corruption that is in the world through lust" (2 Peter 1:4).
*Corruption is deeper than pollutions/defilements on the outside: it is decay on the inside.
Having the knowledge of Jesus Christ does not save a person if there is no heart submission to that knowledge. The latter end is worse than the beginning for these men because rejecting this knowledge will make them more accountable at the judgment.
Faith perfected by works means bring to maturity, carry to the end, to complete like love in 1 John 4:18. It doesn't mean that Abraham was finally saved based on his works in Genesis 22. When Abraham performed the good work in Genesis 22; he fulfilled the expectations created by the pronouncement of his faith in Genesis 15:6.
Nothing here about salvation by works.
So how much obedience does it take? How much obedience must we accomplish and "add as a supplement" to Christ's finished work of redemption in order to help Him save us? We are saved by true faith that trusts exclusively in Christ for salvation and true faith results in obeying God. Faith is the root of salvation and obeying God after we have been saved through faith is the fruit.