For the ANSWER to Which Sin is Worst?
The sin of disobeying Allah subhana wa ta’ala’s Order (an Obligation) – e.g. not doing salah… i.e. ‘Do This!’ – but you don’t:
This sin can be best exemplified as follows: When the angels gathered to witness the creation of Adam (peace be upon him) and then Allah, Most High, ordered everyone to bow down (out of respect) to Adam (peace be upon him). Only one objected – and this was Iblis. He failed to follow a clear-cut order of Allah, Most Exalted.
“And (remember) when We said to the angels: “Prostrate yourselves before Adam.”. And they prostrated except Iblis (Satan), he refused and was proud and was one of the disbelievers (disobedient to Allah).” (Qur’an 2:34)
The Result? 1) He became the accursed (Shaytaan); 2) He is still not repentent (which will serve only to exacerbate his punishment on the Day of Judgement); 3) His arrogance prevents him from recognising the error of his ways because he is convinced he is right.
The sin of doing an act that Allah subhana wa ta’ala has forbidden (a Warning) – e.g. doing zina (a great sin) i.e. ‘Don’t Do This!’ but you do:
This sin can be best exemplified as follows: When Adam (peace be upon him) was told by Allah, Most High (though he was allowed to eat from every tree, he was) not to eat from one specific tree. But despite this warning, Adam (peace be upon him) decided (eventually) to eat from that specific tree. He failed to heed a clear-cut warning from Allah, Most Exalted.
“O Adam dwell with your wife in the Garden and enjoy as you wish but approach not this tree or you run into harm and transgression” (Quran 7:19)
“So by deceit [Satan] brought them to their fall: when they tasted the tree their shame became manifest to them…” (Qur’an 7:21)
‘Our Lord we have wronged ourselves. If You forgive us not and bestow not upon us Your Mercy, we shall certainly be of the losers’ “ (Quran 7:23)
“Thus did Adam disobey his Lord, so he went Astray. Then his Lord chose him, and turned to him with forgiveness, and gave him guidance.” (Quran 20:121-122)
The Result? 1) He was punished; 2) He still possessed the ability to repent (istighfar and towbah) which he most sincerely did; 3) Allah, Most High, accepted his repentance and forgave him.
It is worse not to follow an Order of Allah, the Most High, than to not heed a warning. Yes, both are sins. Both are bad in the end for the one sinning – BUT the danger with the first is it can take you into kufr (like Shaytaan) – and the favour/ opportunity (given by Allah, Most High) to repent may be lost; whilst the second is a sin – sure – and best to avoid – but one remains within the remit of ‘being Muslim’ and so one still possesses Allah, Most High’s favour/opportunity to repent – alhamdulillah.
So, though it is true that the standard idea most of us have of sinning (which is the second category – i.e. the Warning variety) is a bad thing (e.g. do not drink alcohol, do not steal, do not commit zina etc) – many people seem not to be aware of the greater necessity given to avoiding the other (greater) type of sinning – i.e. the Obligation variety (e.g. to establish salah, to pay the zakat etc).