Sin or what makes us a sinner is...
1. Lawlessness
"Whoever commits sin also commits lawlessness, and sin is lawlessness." 1 John 3:4 NKJV
2. Anything that falls short of God's glory:
"For all have sinned and fall short of the glory of God," Romans 3:23 NKJV
3. Knowing what is good to do and not doing it.
"Therefore, to him who knows to do good and does not do it, to him it is sin." James 4:17
4. Whatever is not of faith. So being unsure if something is sin or doing something without the focus being on God.
"But he who doubts is condemned if he eats, because he does not eat from faith; for whatever is not from faith is sin." Romans 14:23
5. Various other forms.
"Therefore put to death your members which are on the earth: fornication, uncleanness, passion, evil desire, and covetousness, which is idolatry...But now you yourselves are to put off all these: anger, wrath, malice, blasphemy, filthy language out of your mouth." Colossians 3:5, 8
6. Pride
"A haughty look, a proud heart, and the plowing of the wicked are sin." Proverbs 21:4
7. Being born Human
"Therefore, just as through one man sin entered the world, and death through sin, and thus death spread to all men, because all sinned." Romans 5:12
8. Foolish planning
"The devising of foolishness is sin, And the scoffer is an abomination to men." Proverbs 24:9
9. Unrighteousness
"All unrighteousness is sin," 1 John 5:16
10. Breaking the 10 Commandments.