The Heroine is My Stepsister, and I'm her Final Boss - Chapter 1: Despair and Death.

Shao Qing’s only regret in life is that she blindly fell in love with a worthless man. She gave up everything for him, but in exchange was run over by his conniving mistress when she was close to her delivery date. Fortunately, Heaven left her a way. Crimson rain fell from the sky, the end of the world arrived, she resurrected in the morgue and gave birth to a little monster. Turning into a half human, half zombie freak; her son neither human, nor monster; they have no other choice but to rely on zombies’ crystal nuclei to develop their special abilities and continue living. This debt, she’ll definitely repay that cheating couple!

- Description from Novelupdates

The Mc reincarnates in a world of magic and adventure as a Leech, follow his adventure in this mysterious and exciting world as he goes from the weakest creature to the shadow being that everyone is afraid of. Will he pursue the path of strength alone? Or without realizing it he will become the king of the greatest empire that ever lived.

Fifty years ago, the oxygen in the atmosphere changed, giving rise to a new form of air known as Spiritual Qi. Humans, plants, and animals alike suddenly awakened latent mutant genes and began evolving, gaining Superpowered Talents and Classes. Life took a new turn, and humanity had to adapt.Everything seemed to be going well until, fifty years later, a 16-year-old boy named Klaus awakened a terrifying Talent and Class. His awakening marked the beginning of a new era in human evolution.Unbeknownst to everyone, Klaus, who was shunned by society and dropped out of school to work for a better life for himself and his mother, was actually the last of the Nine Paragons—a being so powerful that even the heavens feared him.Watch as Klaus climbs the ladder of strength, pursuing absolute power with a single purpose: to protect and make his mother happy.

"One Sin can destroy a man..."

Azekiel, a young man, was forced to embrace his death simply for one small sin... the sin of Hunger.

It was only when he paid the price for his hunger with his life that he realized the cruelty of this world.

Watch Azekiel embrace the hunger that brought forth his demise as he walks on a path of total domination in the Tower of Sins, becoming the Seventh King of Sin: The King of unsatiable Gluttony!

......

The Tower of Sins... A majestic Tower that appeared in the world just as the world had lost all hopes.

Humanity was near extinction in the apocalypse brought forth by the appearance of Monsters in the once peaceful world. Their last hope... The mystical tower that had appeared out of nowhere became the shelter of humanity.

The humans that took shelter in the tower were many; amongst them were a few that were selected by the Tower itself. These Humans were known as the Lord of Sins, who received abilities from the tower itself.

As for what abilities, no one knew... All people knew was that the abilities they received were related to the biggest sin they committed in life. They were all given one task... Climb the tower and reach the top to receive incredible strength and freedom.

Only Lord of Sins and the people they selected were authorized to climb and go up, facing hardships. They were the gods of the Tower! The rest... They were left behind on Floor Zero. Amongst the humans left behind was Azekiel... A human who had never committed even a single sin in his life. Until...

A single sin can change a person's life. What happens when a good man commits a sin worthy of making him a Lord of Sin?

The legend of Sins is about to unfold that can threaten reality itself, bringing forth many unimaginable secrets of the world!