Jiang Chenyu's mission is to travel between different worlds and raise the protagonists' corruption levels. But something goes wrong: their corruption levels skyrocket, throwing the worlds into turmoil, and he has to return to those small worlds to lower them.
Modern World:
Jiang Chenyu is a profit-driven, bottom-tier actor. The first thing he does after winning the favor of a powerful patron is dump the impoverished protagonist. He then makes a name for himself, rising to stardom and taking the internet by storm.
The protagonist hates him to the point of gritting his teeth. Ten years later, he returns triumphant as the heir apparent of the capital. When the truth about what happened back then comes to light, Jiang Chenyu falls from grace, reviled by everyone and left with nowhere to turn. Just then, the protagonist appears. "Jiang Chenyu, do you regret it?"
Ancient World:
Jiang Chenyu is a noble and refined Imperial Tutor. At the crucial moment in the struggle for the throne, he does not hesitate to stab the protagonist, betray him in public, and join the villain, helping him become emperor. Jiang Chenyu himself rises to become the chancellor, second only to the emperor and above all others. He becomes The Outcast.
Later, the protagonist captures the imperial capital and has the villain beheaded in public. But he spares Jiang Chenyu, who betrayed him, and confines him in his bedchamber, tormenting him as he pleases. Finally, he bites down on Jiang Chenyu's neck, eyes red as he demands, "Teacher, why did you betray me?"
Apocalyptic World:
Jiang Chenyu is the most accomplished researcher in the apocalypse. To survive, he chooses to abandon everyone at the base and defect to their rival, watching the protagonist's base fall without lifting a finger.
At the point of despair, the protagonist awakens a supernatural ability and turns the tide. Before long, he uses his overwhelming strength to establish a new base. Meanwhile, Jiang Chenyu's base suffers heavy losses in a zombie attack. When the protagonist hears about it, he says, "If you want me to help, hand Jiang Chenyu over to me."
In the Miaojiang story:
Jiang Chenyu is the eldest young master of a wealthy family. He falls in love at first sight with the protagonist, a Miaojiang sorcerer, and sweet-talks him into leaving his village and giving up everything to come to the city with him. But before long, Jiang Chenyu grows tired of him and dumps him without a second thought.
The protagonist hates Jiang Chenyu to the bone and chooses to return to his village and become a sorcerer again. Because Jiang Chenyu was faithless, the Gu poison in his body flares up, leaving him gravely ill and unable to recover. He has no choice but to go beg the protagonist for help. The protagonist's expression darkens as he smiles with obsessive intensity. "I knew it. Big Brother still loves me. You came back to me after all."
In the Immortal Cultivation World:
Jiang Chenyu is a compassionate Immortal Venerable, but in a moment of crisis, he abandons the protagonist to save the younger disciple he favors, watching helplessly as the protagonist falls into the demon abyss and is devoured by evil spirits.
A hundred years later, the protagonist fights his way out of the demon abyss, fueled by hatred, and becomes a Demon Venerable feared far and wide. He binds Jiang Chenyu's hands and feet with iron chains and holds a sharp knife in his hand. "Master, do you want to save your beloved young disciple? Then please me."
Reader's Guide:
1. As always, expect melodramatic angst, love and hatred, passionate entanglements, and a fake forced-romance trope.
2. The protagonist appears to be forced, but secretly enjoys it. It doesn't hurt him, and he isn't really abused. All those tragic scenes are just him acting.
3. It's a fake forced-romance trope. The protagonist is adored by everyone, while the love interest darkens with unrequited love and goes completely off the rails in all kinds of ways.
4. The protagonist's misdeeds will be whitewashed later on, and the love interest will wail and regret everything. So it's probably the protagonist who suffers early on (but it doesn't hurt him; he's just pretending), and the love interest who suffers later (and that part is real).
5. If you share my tastes, come on in!
Theme: Mutual love is the only true love.