The upcoming chapter of "Fairy Tail" is predicted to deliver the reason why Meliodas betrayed the Demon Clan and killed two of the Ten Commandments' members. Although unconfirmed, majority of the manga's followers believe Meliodas did such things for his love for Elizabeth.
In chapter 200 entitled, "Memories of the Holy War," it was revealed that contrary to what King and Diane thought, Dolor and Gloxinia only pretended to attack them. In the end they were really planning to help improve the strength and capabilities of the King's Holy Knights. This was evident when the two were healed by Dolor and Gloxinia using their powers.
Confused with what just transpired, both King and Diane asked questions as they thought Dolor and Gloxinia are part of the Demon Clan. The latter then explained they were once part of the group but several events took place which convinced them to leave the organization.
Convinced with the explanation, King and Diane agreed to be trained by their former opponents. This led to them to being transferred into Dolor and Gloxinia's bodies. The succeeding events featured Dolor, who is occupied by Diane, and Gloxinia, whose body is used by King, meeting with Meliodas and Elizabeth. In awe and disbelief, King and Diane suddenly realized they are about to witness memories from the past, memories coming for the Holy War that took place several years ago.
Meanwhile, fans over at Reddit are delighted with the events showcased in chapter 200. Since it was already revealed that the pinnacles of the four races were actually close friends before, majority believes that Meliodas betrayed his clan because of his love for Elizabeth the goddess.
On the other hand, another fan believes that chapter 201 will feature how the four made a pact to end the Ten Commandments if they ever make it back to the world. While Meliodas' past is unknown, he is known to be the next Demon King, Nanatsu No Taizai Wikia described.
Unfortunately, despite being one of the most evil, vile and terrifying demon ever existed, Meliodas fled from his clan and betrayed them by killing Aranak and Zeno. Up until this moment, his reasons for committing those actions are still a mystery.
For an in-depth review of the previous chapter, check the video below.