In my religious background, there is huge emphasis on fearing God, fearing His wrath, and hell. Hell is very graphical. Here are some verses showing how graphical it is:
"And if ye do it not - and ye can never do it - then guard yourselves against the Fire prepared for disbelievers, whose fuel is of men and stones." (Q 2:24) "Lo! Those who disbelieve Our revelations, We shall expose them to the Fire. As often as their skins are consumed We shall exchange them for fresh skins that they may taste the torment. Lo! Allah is ever Mighty, Wise." (Q 4:56) "For such, their habitation will be hell, and they will find no refuge therefrom" (Q 4:121) "Lo! the hypocrites (will be) in the lowest deep of the Fire, and thou wilt find no helper for them;" (Q 4:145) "Lo! those who disbelieve and deal in wrong, Allah will never forgive them, neither will He guide them unto a road, Except the road of hell, wherein they will abide for ever. And that is ever easy for Allah." (Q 4:168-169) "They will wish to come forth from the Fire, but they will not come forth from it. Theirs will be a lasting doom." (Q 5:37) "Theirs will be a bed of hell, and over them coverings (of hell). Thus do We requite wrong-doers." (Q 7:41) "O ye who believe! Lo! many of the (Jewish) rabbis and the (Christian) monks devour the wealth of mankind wantonly and debar (men) from the way of Allah. They who hoard up gold and silver and spend it not in the way of Allah, unto them give tidings (O Muhammad) of a painful doom, On the day when it will (all) be heated in the fire of hell, and their foreheads and their flanks and their backs will be branded therewith (and it will be said unto them): Here is that which ye hoarded for yourselves. Now taste of what ye used to hoard." (Q 9:35) "Know they not that whoso opposeth Allah and His messenger, his verily is fire of hell, to abide therein ? That is the extreme abasement." (Q 9:63) "Hell is before him, and he is made to drink a festering water, Which he sippeth but can hardly swallow, and death cometh unto him from every side while yet he cannot die, and before him is a harsh doom." (Q 14:16-17)
Even though I have left this religion but I get this nightmare that I am getting punishment for leaving the religion. I feel scared that what if I am wrong and end up burning in hellfire.
How to get rid of this fear so that I can live my life freely?
My only crime was that I became more religious than them in my early childhood out of my own devotion and I became a poster child for piety. It all starts to disappear when I left my sect first, then I start to listening music and being clean shaved.
That's shitty man.
I'm lucky enough that most of the people that have mistreated me in my life haven't been monsters, just people in a different position than me or maybe with different priorities. I found it much easier to forgive my middle school bullies for example when I considered that they were also vulnerable kids trying to fit in.
It's unfortunate that the way they did that was by pushing me out and ostracising me (and hurting me) but it feels so much better to forgive them than it did to bitterly hold a grudge.
Your parents are probably also afraid of hell, and feeling guilt for having "failed you". They probably get judged by their peers for not "raising you properly". You should be proud of your commitment to escape this cycle of trauma. Maybe instead of resentment you could pity them. Or maybe you can be grateful that despite all the ways they mistreated you, they raised you in a way that allowed you to develop critical thinking skills and break the cycle of trauma.
Or not.
I don't know your situation I'm just skeptical that holding onto resentment is going to give you good results, but I'm not a psychologist.
Some people don't deserve kindness. I think I can at least hate them in my heart if I cannot take physical action against them