The heroes and titular characters of the Seven Deadly Sins universe are memorable for the unique abilities and gifts that they bring to the table. Each of them was responsible for saving the day in one regard or another during the war against the forces of the wayward holy knights and Demon King. Further, the Sins embodied the bond and unity of mortal races.
However, they vary dramatically in usefulness throughout the overarching narrative. By ranking the heroes based on how invaluable they were to the plot, we can better appreciate their contributions - or lack thereof.
7 Diane's Giant Stature Hides How Weak She Actually Was
Despite being one of the first of the group to have recovered her Sacred Treasure, Diane's contributions to the heroes' cause were minimal. She was subdued by the knights of Liones once before and almost immediately dominated during the fight against Drole and Gloxinia.
Although Diane has proven useful in minor aspects throughout the story (such as the assistance she lent to Matrona against human mercenaries), the value she actually contributes to the Sins as a collective is depressingly minimal.
6 Gowther's Abilities Are Extremely Specific, & He Has Sabotaged The Team Before
Gowther was one of the few members of the Sins to have actively sabotaged his own organization. He was responsible for erasing Diane's memories, thereby setting back her relationship with King in a heartbreaking way. Additionally, the Lust sin was also responsible for shooting down Escanor during Drole's tournament.
Although he lacks the brute force of his comrades, Gowther's memory-inducing (and stealing) arrows have proven situationally useful. It saved the group from being massacred by Galand and helped to redeem Mael during his crisis of identity.
5 King Was Extremely Powerful In His Evolved State
Despite his timid disposition, King was invaluable to the efforts of Meliodas and his comrades. He was responsible for identifying the mystery behind Helbram and defeating him in a climatic battle.
Not only did he help to save his forest from a demonic invasion, but King also held his own against Mael even after the man had swallowed several of the commandments. In his evolved state, his configurations are as deadly as they are versatile. He proved to have earned Gloxinia's blessing as a deserving ruler of the fairy race when combatting Zeldris and the original demon from long range in the battle to protect Merlin.
4 Merlin Provided Mystical Solutions To Difficult Problems
As perhaps the most powerful mage alive, Merlin was an excellent asset to the Sins. Her expansive arcane knowledge allowed her to create perfect cubes that could withstand staggering damage, and when necessary, even hold a demonically corrupted Meliodas.
Merlin's immortality (as well as the boons she had conned from the Supreme Deity and Demon King) made her one of the only characters capable of defeating Grayroad. She also contributed to the fight against Zeldris in the final battle and was nearly even able to stop the possession of Meliodas' body through a time-halting incantation.
3 Escanor Was Immensely Powerful Under The Right Conditions
During the day, Escanor was a nearly unstoppable juggernaut. His Grace allowed him to exude such immense quantities of sunlight that it could evaporate entire lakes with a single blast.
He was strong enough to make Commandments flee in terror, powerful enough to dominate both Estarossa and Zeldris simultaneously, and fast enough to dodge a flurry of Ludociel's attacks. In addition to being the Sins' best straightforward brawler, he also managed to contain Meliodas after his corruption and trade blows with the original demon.
2 Meliodas Managed To Overcome Liones' Corruption, Lead The Sins, & Defeat The Demon King
Meliodas was the captain of the Sins and a man who contributed to its success immensely. Not only was he responsible for reassembling the group after they became fugitives, but he also managed to defeat Hendrickson, clearing his friends' names and undoing the systemic corruption of Britannia.
Additionally, Meliodas fought and ultimately defeated the Demon King in order to regain control of his own body. However, his overzealousness and subsequent corruption both detract from how useful he can be to the heroes' efforts, especially since his physical body was weaponized against them in the final battle.
1 Ban Saved Meliodas, Fought Multiple Commandments, & Even Battled The Demon King Himself
Despite his roguish demeanor and devil-may-care attitude, Ban is the most useful member of the Seven Deadly Sins. He fought many members of the Ten Commandments, including Galand, Melascula, Estarossa, and even Meliodas.
Not only was he successful in saving both Elaine and Jericho, but he also held off the Demon King while the captain battled for control of his body - all without the blessing from the fountain of youth. Ban may have blundered when turning against Meliodas in the attack on Hendrickson's castle, but he altered his course before irreversible damage could be done.