We are always culpable to some extent for sin.
Always.
Now, when a person plans a murder, it is a more serious sin than if a person murders out of anger. However, anger is a sin to begin with and one is culpable for harboring anger and not dealing with a violent nature.
The Catholic Church teaches that God gives grace to all persons for salvation.
We may have circumstances which ameliorate certain levels of responsibility, but we are always responsible to some extent.
One of the greatest heresies now is the denial of free will.
We cannot psychoanalyze away sin, Sin is against reason. That is the problem with so many people who want to rationalize away sin. They cannot do so.
When we die, God is not going to ask us how remiss our parents were in teaching us the Catholic Faith. That omission will be part of the parents' particular judgment.
We see our sins and basically judge ourselves in the light of truth.
See the other posts on general and particular judgment.
And, from the CCC.
II. THE DEFINITION OF SIN
1849 Sin is an offense against reason, truth, and right conscience; it is failure in genuine love for God and neighbor caused by a perverse attachment to certain goods. It wounds the nature of man and injures human solidarity. It has been defined as "an utterance, a deed, or a desire contrary to the eternal law."121
1850 Sin is an offense against God: "Against you, you alone, have I sinned, and done that which is evil in your sight."122 Sin sets itself against God's love for us and turns our hearts away from it. Like the first sin, it is disobedience, a revolt against God through the will to become "like gods,"123 knowing and determining good and evil. Sin is thus "love of oneself even to contempt of God."124 In this proud self- exaltation, sin is diametrically opposed to the obedience of Jesus, which achieves our salvation.125
1851 It is precisely in the Passion, when the mercy of Christ is about to vanquish it, that sin most clearly manifests its violence and its many forms: unbelief, murderous hatred, shunning and mockery by the leaders and the people, Pilate's cowardice and the cruelty of the soldiers, Judas' betrayal - so bitter to Jesus, Peter's denial and the disciples' flight. However, at the very hour of darkness, the hour of the prince of this world,126 the sacrifice of Christ secretly becomes the source from which the forgiveness of our sins will pour forth inexhaustibly.