Chapter 25, King was revealed to be the king of the fairy's 700 years ago by Elaine.
Chapter 28, Meliodas is hinted to be extremely dangerous via his shadow.
Chapter 29, Meliodas is revealed to have destroyed the Kingdom of Danafor in the past when he lost control.
Chapter 30, The Demon Ban killed in his backstory is being used to empower the second generation of Holy Knights.
Chapter 32, Elizabeth is revealed to have come from the Kingdom of Danafor that Meliodas destroyed.
Chapter 51, Meliodas revealed that the whole time he was fighting, he was holding back his power to which he shows by cutting a small mountain with just a branch he found and he know more about the upcoming Holy War.
Chapter 54, the nerdy looking kid Armando, was in fact Gowther the whole time and he had a girly looks as well.
Chapter 60, We find out there's another princess being hidden away and she knows full well the Holy Knights are the ones causing trouble. What's more we finally get the true goal of the Holy Knights, to unlock the seal of the Demon Clan just to start a war in the kingdom they can fight in. Yeah that seems like a great idea.
Chapter 62: King Arthur and his huge army arrive in Lyonesse.
Chapter 70, The up to now Comically Serious effeminate-looking Gowther reveals that he has a darker side as he completely Mind Rapes Dreyfus with his ability "Nightmare Teller".
Chapter 73 King and Diane spent five hundred years together before he erased her memory.
King's Backstory, King and Diane's relationship is revealed to be actually deeper than it initially appeared.
Chapters 81-82, In the midst of a battle against Gilthunder, Hendricksen, and the Masked Female Holy Knight, Meliodas attacks some sort of monster that was accompanying Princess Margaret completely hidden from sight. Though this forces Meliodas to take a hit and become wide open to an attack from Hendricksen, Gilthunder of all people comes to Meliodas' aid. It's then revealed that Gilthunder was actually forced to do vile deeds because Margaret had been taken hostage, his Badass Boast of being stronger than any of the Sins was actually a Survival Mantra taught by Meliodas to give Gil courage should he be in a desperate situation, and because said "Courage Charm" was taught by Meliodas, the latter was able to deduce that Gil was in such a situation right away way back when they reunited in the forest where Diane hid. Furthermore, Gil completely knew of the scheme to frame the Sins back then but was forced not to say anything. Gil also knew the true perpetrator of his father's murder and with Margaret safe, he releases all his pent-up wrath and completely obliterates Hendricksen.