God only imputes sin on living things that have a creative mind capable of reasoning, making choices, and who possess (at minimum) a basic understanding of the difference between good and bad. Beings such as humans and angels meet these criteria, although there does exist a large subset of humans that are not held accountable concerning transgressions. Additionally, there are many things made by the Eternal (in spite of the pain and sufferings they can sometimes cause) that he does not impute any disobedience.
Inanimate (lifeless, inorganic) objects cannot sin because they do not possess a mind and therefore cannot make choices. This large class of objects includes everything from rocks to clocks and grains of sand to entire galaxies. They behave and interact based on physical laws placed in motion when everything was created.
Plants, although they are alive, cannot sin as they lack a mind and therefore cannot reason. Their existence (how they grow, adapt, etc.) is governed, like inanimate objects, based upon rules put in place before their initial creation. Animals, even though they (in varying degrees) possess the ability to adapt and learn, also cannot transgress God's law. Their lives, which can exhibit complex behaviors, are governed by a sophisticated program placed in each of them we call instinct.
Humans in the womb, babies and young children (up to the time they begin to understand the basic difference between good and bad) do not have sin imputed to them. For example, the Apostle Paul states that God determined Esau would serve Jacob before they were born and had any chance to do good or evil (Romans 9:11 - 12).
Scripture does offer evidence to an "age of accountability" when God (no doubt on an individual basis) considers a human capable of understanding right from wrong and therefore able to sin. When the ancient Israelites became fearful and refused to go, as commanded, into the Promised Land, they were punished by wandering the desert for 40 years (Numbers 13 - 14, Deuteronomy 1:26 - 28). Those considered old enough to understand and reject His command never entered the "land of milk and honey." The Lord declared, however, that children who "in that day had no knowledge between good and evil" would be allowed to eventually enter the promised inheritance (Deuteronomy 1:39 - 40).
The English word "sin" occurs 336 times in the KJV Old Testament and 112 times in the New. Synonyms such as "wickedness" are found 127 times in the King James Bible, with "transgression(s)" occurring 99 times, "trespass" used 82 times and "evil" occurring a whopping 613 times!
Surprisingly, the first occurrence of the word "sin" in the KJV is not made in reference to Adam and Eve's disobedience in the Garden of Eden. It is first used concerning their firstborn child, Cain, when God personally warns him about his negative attitude after his offering was deemed unacceptable (Genesis 4:6 - 7).
The first being to commit a sin is Lucifer, one of only three named angels in the entirety of God's word. Jesus called him a murderer and a being who does not retain a shred of truth in his heart. He is also referred to as the father of lies (John 8:44), meaning he is the first created being to communicate information to others that he KNOWS is wrong!
Apart from Satan and his demons, who are the worse sinners mentioned in the Bible? BibleStudy.org's list of the most evil folks in the Old Testament include an Egyptian Pharaoh (the one who refused to let the children of Israel free from slavery), Israel's King Ahab and wife Queen Jezebel, plus the Kings Ahaz, Manasseh and Queen Athaliah who ruled the Kingdom of Judah. Others who indulged in great evil include Haman (wanted to mass exterminate the Jews), Doeg (murdered priests of God) and Abimelech (killed seventy brothers).
Our picks of "chief sinners" in the New Testament include Herod the Great and his son Herod Antipas, Judas Iscariot, Simon Magus (Simon the Sorcerer), Saul (before he became the apostle Paul), and the end time Beast and False Prophet.
The unpardonable sin is not a single disobedient act or thought committed by a person. It is the willfull rejection of God made by anyone who previously understood the truth. The ultimate penalty for such an attitude will be destruction, with no hope of a resurrection, in the lake of fire. It should be noted that such an attitude is considered "unpardonable" not because our heavenly Father will not forgive it, but because the person maintaining it REFUSES to repent of their rebellion and instead makes themselves a hardened enemy of righteousness!