In The Seven Deadly Sins, the Holy Knights are Liones's protectors, sworn to defend the country and throne from its many threats. Combating enemies external and internal, they are the first line of defense against any which might do the kingdom harm, comprising the bulk of the knight force during the New Holy War.
Despite the prestige attached to their name, the history of the Holy Knights is not a spotless one. While some of them may be paragons of their Order, others ~ through immorality or incompetence ~ have stained what it means to serve Liones. To understand the Knights the best, we observe some examples.
10 Dishonorable – Marmas
This rotund, beetle-like man's ability is to shake his maracas, increasing the gravity around the target of his choice. It was enough to fell Diane during his confrontation with her outside the Fight Festival, despite the Sin's attempt to rescue an innocent person.
Perhaps more egregiously than Marmas's thoughtlessness is his incompetence. During the attack by the Ten Commandments on Liones, he removed his armor on account of not wanting to deal with Escanor's heat. Consequently, it made him a gigantic, fleshy target for his enemies, and accordingly, he would not survive the invasion.
9 Honorable – Howzer
Howzer places chivalry and honor above all else. He was among the first of the Holy Knights to realize that the Sins were not evil and to attempt assisting them, co-operating with Diane to rescue an innocent person from collateral damage.
Moreover, Howzer's wind attacks are incredibly potent. They were enough to make Estarossa flinch and recoil despite having absorbed the power of the other Commandments (roughly at around 88,000). This would save more innocent lives at the risk of his, embodying the virtues of what it means to be a knight.
8 Disgrace – Golgius
A member of the notorious "Weird Fangs," Golgius's methods and objectives are among the most dishonorable tactics ever employed by Liones. He attempted to lie to the Sins about his ability (claiming it was teleportation when it was actually invisibility), used poison on Meliodas, and would only strike at his opponents when he thought they were unaware of his proximity.
Fortunately, the power disparity between Meliodas and a slightly above average knight was considerable enough that he would be able to survive this, even in his weakened state. Nonetheless, Golgius's tactics are a disgrace to the Order.
7 Honorable – Gilthunder
Gilthunder is possibly one of Liones's most capable knights. He is able to exert large torrents of lightning against his foes, proving a challenge even for Meliodas himself on their first encounter and being one of the few knights to make the Captain concerned.
Gilthunder's courage matches his skill. When Margaret was possessed by Ludociel in a consensual contract to guarantee his freedom, he was immediately horrified and distrustful of the Archangel. To ensure that no treachery would be had, he agreed to follow him in confronting Meliodas ~ along with three of the most deadly lieutenants in the Demon King's army.
6 Dishonorable – Vivian
One of the most maniacal members of the Holy Knight order, Vivian's unhealthy, irrational obsession with Gilthunder compels her to resort to any lengths to obtain him. This includes dealing with demons, attacking the Sins, and even flagrantly abducting Gilthunder herself.
Having apprenticed under Merlin, Vivian had the mystical potential to serve Liones well, especially in her mistress's absence when assisting Camelot. Disregarding her tenuous sanity, few can attest to the arcane skill she wields. Unfortunately, Vivian squandered it in her obsession, one which would ultimately cost her her life.
5 Honorable – Guila
Guila's actions, from fighting the Seven Deadly Sins to imbibing the demon blood, was for a single purpose: Protecting her little brother, Zeal. Though she may have been one of the Sins' most dogged adversaries, this was only due to the manipulation of Hendrickson (who in turn was possessed by Fraudrin at the time).
Despite the lengths she was willing to deign for victory, Guila's ambitions justify the decision she made. Guila would show remorse for attacking the Sins after their nature was revealed, leading the charge against the Ten Commandments and almost being slain by Estarossa.
4 Dishonorable – Twigo
Twigo is a force of nature, able to rip apart forests with a single blow. Unfortunately, he is not a force for good or even one for Liones. When he was sent on a mission to retrieve Elizabeth, he showed little concern for the Princess's safety, even inclined to kill her amidst his frenzy against Meliodas.
Despite Twigo's terrifying power, he is bloodthirsty even without demonic corruption. In conclusion, he is a stellar example of why a formidable knight does not equate to a righteous one.
3 Honorable – Jericho
Insecure and somewhat unhinged, Jericho has faced a difficult past. When she claimed she was "reborn" after drinking demon blood and embracing her gender, Jericho painted her lips in blood to embody this transformation.
Similarly to Guila, the revelation of the Sins' true nature elicited a new transformation, one which turned her from a quarrelsome psychopath into a loyal ally. She would help Ban against the combined forces of Galand and Melascula, proving that redemption is available for those who seek it.
2 Dishonorable – Ruin
Ruin delighted in the suffering he inflicted on his enemies, especially by the way he turned Diane and Meliodas against one another. Through these manipulations, he was able to destroy two enemies at once, cackling in satisfaction as they fought for his amusement.
Fortunately, Elizabeth saw through the trick and was able to remove the bell of Ruin's staff, banishing the illusion and resulting in his swift defeat and imprisonment. Despite Ruin's bluster and haughty mannerisms, he is quick to fall in a fair fight.
1 Honorable – Dreyfus
The proud father of Griamore and a Grandmaster of the Holy Knights, Dreyfus's heroism is limited only by his ability. He was willing to confront Hendrickson after he learned of the latter's corruption, despite being drastically outmatched by the power of a Commandment.
Though Dreyfus would be made into a pawn against his will, Fraudrin's occupation of his body did not inflict half as much damage as he did under Hendrickson. Once Dreyfus's senses returned to him, he would continue to lay down his life for the sake of his allies, including saving his son during the second Holy War.