What are the top 10 worst sins you can commit?
Allah says in the Qur'an:
“If you avoid great sins which you are forbidden, We will expiate from you your (small) sins and cause you to enter an honorable (place of) entering. (Surah 4, Verse 31).
Therefore, a mukallaf must know which sins are great, so that he/ she desists from them. In this way, Allah, in His mercy and according to His promise, will forgive all his minor sins and mistakes.
The following list of the great sins is taken from Minhajus Saleheen (of Ayatullah Sayyid Abul Qasim al-Khoui, Dama Zilluhu):
To believe that Allah has any partner or colleague in His Divinity; to worship someone besides Allah.
To lose hope in the mercy of Allah; to believe that Allah would not save him on the day of judgement.
To have no fear of Allah; to think that Allah would not punish him for his sins.
To misbehave with parents; disobeying them or injuring their feeling.
To kill someone unjustly, i.e. without permission of sharia.
To slander a married woman, accusing her of adultery.
To eat an orphan's money or property unlawfully and unjustly.
To flee from jihad (religious war).
To use or eat a thing or money obtained as interest.
Fornication and/or adultery.
Homosexuality (whether between males or females).
To swear falsely by name of Allah.
To neglect prayer (Salat) or any other wajib thing.
To withhold zakat.
To give false evidence.
To hide (i.e. not to give) true evidence.
To drink intoxicant, liquor.
Breach of promise.
To misbehave with blood-relatives; not doing good to them.
To migrate to a place where there might be a danger to religion or to its observance - i.e. where one would not be able to follow the rules of sharia without hindrance.
Theft or robbery.
Rejection or denial of what Allah has revealed to the Prophet (s.a.w.a).
To tell a lie; even more grievous is a lie against or about Allah, the Holy Prophet (s.a.w.a.) or the Imams (a.s.).
To eat meat etc., of a dead animal, or of one not slaughtered according to the rules of sharia.
To drink or eat blood.
To eat pork, lard or any part of a pig.