ANSWER: The Bible does not have a list called 'the seven deadly sins.' A Catholic Church monk around the 4th century A.D. likely started this list. It is not so much a collection of the worst offenses man can commit, as it is a list of what Roman Catholics consider are the worst attitudes that are the basis for all disobedience to the Eternal. The most common list of seven attitudes considered deadly are wrath, greed, lust, pride, envy, sloth and gluttony.
The nearest thing in the Old Testament to a list of seven sins considered deadly is in the sixth chapter of the book of Proverbs. Solomon writes that God hates those who is full of pride, a liar, a murderer of those who are innocent, a person who devises ways to do evil and those who are eager to do wrong. He also hates those who bear false testimony against another person and those who seek to pull people apart through sowing seeds of contention (Proverbs 6:16 - 19). The only thing clearly in common, however, between the list of what God hates and what Catholic's believe are the seven worst sins is the attitude of pride.
The New Testament has at least two lists that delineate several, but not exactly seven, sins. The first list is found in 1Corinthians 6:9 - 10. The apostle Paul states that adulterers, thieves, drunkards, extortioners, the covetous and so on will not receive eternal life. The second list, found in Galatians 5:19 - 21, states that those who practice fornication, idolatry, sorcery, spreading dissensions and heresies, contentious behavior and still others will NOT be in God's kingdom!
Ultimately, the Bible teaches that sins, which it defines as the transgression of ANY of the laws of God, if unrepented of will bring the penalty of eternal death. We might grade them but God does not, as ANY one of them is deadly! The apostle John states, "And by this standard we know that we know Him: if we keep His commandments. 4. The one who says, "I know Him," and does not keep His commandments, is a liar, and the truth is not in him" (1John 2:3 - 40).
The book of Galatians states (as well as many others) that all mankind, from the greatest to the least, sins. The book of Romans further specifies that those who do so must pay with their lives (Galatians 3:22, Romans 6:23)!
Thankfully, God has provided a way to be forgiven, through the unselfish sacrifice of Christ (Romans 5:8). He does not forgive us only seven times (the number Peter thought was the upper limit to him forgiving others, see Matthew 18:21) but is gracious and merciful to overlook our trespasses as many times as it takes (verses 21 - 22)! Our heavenly Father even promises there will come a time when He will decide NOT to remember our sins FOREVER!
No more shall every man teach his neighbor, and every man his brother, saying, 'Know the Lord,' for they ALL shall know Me, from the least of them to the greatest of them, says the Lord. For I will forgive their iniquity, AND THEIR SIN I WILL REMEMBER NO MORE (Jeremiah 31:34)