 
 
The Major Sins 
  --Al-Kaba'r--
  The major sins are those acts which have been forbidden by Allah in the Quran 
  and by His Messenger (SAW) in the Sunnah (practise of the Prophet), and which 
  have been made clear by the actions of of the first righteous generation of 
  Muslims, the Companions of the Prophet (SAW). 
  Allah Most High says in His Glorious Book: 
If you avoid the major (part) of what you have been forbidden 
  (to do), We will cancel out for you your (other) evil deeds and will admit you 
  (to Paradise) with a noble entry. (al-Nisa 4:31)
  Thus by this verse, Allah Most High has guaranteed the Garden of Paradise to 
  those who avoid the major sins. And Allah Most High also says: 
  Those who avoid the greatest of sins and indecencies, and forgive when they 
  are angry (al-Shra 42:37) Those who avoid the greatest sins and indecencies, 
  except for oversights, (will find that) surely your Lord is ample in forgiveness. 
  (Al-Najm 53:32)
  The Messenger of Allah (SAW) said: "The five [daily] prayers, Friday to 
  Friday, and Ramadan to Ramadan make atonement for what has happenned since the 
  previous one when major sins have been avoided." It is therefore very important 
  to determine exactly what the greatest vices, technically called "the major 
  sins" (Kaba'ir), are, in order that Muslims should avoid them. 
  There is some difference of opinion among scholars in this regard. Some say 
  these major sins are seven, and in support of their position they quote the 
  tradition: "Avoid the seven noxious things"- and after having said 
  this, the propeht (SAW) mentioned them: "associating anything with Allah; 
  magic; killing one whom Allah has declared inviolate without a just case, consuming 
  the property of an orphan, devouring usury, turning back when the army advances, 
  and slandering chaste women who are believers but indiscreet." (Bukhari 
  and Muslim) 
'Abdullah ibn 'Abbas said: "Seventy is closer to their number than seven," and indeed that is correct. The above tradition does not limit the major sins to those mentioned in it. Rather, it points to the type of sins which fall into the category of "major." These include those crimes which call for a prescribed punishment (HADD; plural, HUDUD), such as theft, fornication or adultery (ZINA), and murder; those prohibited acts for which a warning of a severe punishment in the Next is given in the Qur'an or the tradition; and also those deeds which are cursed by our Prophet (SAW). These are all major sins.
Of course, there is a gradation among them, since some are more serious than others. We see that the Prophet (SAW) has included SHIRK (associating someone or something with Allah) among them, and from the text of the Qur'an we know that a person who commits SHIRK will not his sin be forgiven and will remain in Hell forever.
Allah Most High says: Surely, Allah does not forgive associating anything with Him, and He forgives whatever is other than that to whomever He wills. (al-Nisa 4:48 and 116)
01. Associating anything with 
  Allah 
  02. Murder 
  03. Practising magic 
  04. Not Praying 
  05. Not paying Zakat 
  06. Not fasting on a Day of Ramadan without excuse 
  07. Not performing Hajj, while being able to do so 
  08. Disrespect to parents 
  09. Abandoning relatives 
  10. Fornication and Adultery 
  11. Homosexuality(sodomy) 
  12. Interest(Riba) 
  13. Wrongfully consuming the property of an orphan 
  14. Lying about Allah and His Messenger 
  15. Running away from the battlefield 
  16. A leader's deceiving his people and being unjust to them 
  17. Pride and arrogance 
  18. Bearing false witness 
  19. Drinking Khamr (wine) 
  20. Gambling 
  21. Slandering chaste women 
  22. Stealing from the spoils of war 
  23. Stealing 
  24. Highway Robbery 
  25. Taking false oath 
  26. Oppression 
  27. Illegal gain 
  28. Consuming wealth acquired unlawfully 
  29. Committing suicide 
  30. Frequent lying 
  31. Judging unjustly 
  32. Giving and Accepting bribes 
  33. Woman's imitating man and man's imitating woman 
  34. Being cuckold 
  35. Marrying a divorced woman in order to make her lawful for the husband 
  36. Not protecting oneself from urine 
  37. Showing-off 
  38. Learning knowledge of the religion for the sake of this world and concealing 
  that knowledge 
  39. Bertrayal of trust 
  40. Recounting favours 
  41. Denying Allah's Decree 
  42. Listening (to) people's private conversations 
  43. Carrying tales 
  44. Cursing 
  45. Breaking contracts 
  46. Believing in fortune-tellers and astrologers 
  47. A woman's bad conduct towards her husband 
  48. Making statues and pictures 
  49. Lamenting, wailing, tearing the clothing, and doing other things of this 
  sort when an affliction befalls 
  50. Treating others unjustly 
  51. Overbearing conduct toward the wife, the servant, the weak, and animals 
  
  52. Offending one's neighbour 
  53. Offending and abusing Muslims 
  54. Offending people and having an arrogant attitude toward them 
  55. Trailing one's garment in pride 
  56. Men's wearing silk and gold 
  57. A slave's running away from his master 
  58. Slaughtering an animal which has been dedicated to anyone other than Allah 
  
  59. To knowingly ascribe one's paternity to a father other than one's own 
  60. Arguing and disputing violently 
  61. Witholding excess water 
  62. Giving short weight or measure 
  63. Feeling secure from Allah's Plan 
  64. Offending Allah's righteous friends 
  65. Not praying in congregation but praying alone without an excuse 
  66. Persistently missing Friday Prayers without any excuse 
  67. Unsurping the rights of the heir through bequests 
  68. Deceiving and plotting evil 
  69. Spying for the enemy of the Muslims 
  70. Cursing or insulting any of the Companiions of Allah's Messenger.