LOL the manga has been all over the place, but assuming we attempt to use logic and ignore some of inconsistencies here it is:
1. Meliodas/DK/Supreme Diety
2. Current Escanor (daytime form near noon)
3. Ban/Wild
4. Mael
5. Zeldris (God Magic + ON)
6. King
7. Sinner
8. Elizabeth
9. Ludoshel
10. Merlin
Honorable mentions:
1. Mother of Chaos - potentially the same tier as the gods, but she is featless outside helping to defeat a weak indura.
2. OG Gowther - He managed to brainwash even the SD and DK, but it costed him his life. In battle he is featless.
Reasoning for placements:
1. Meliodas is the same level as the DK and Supreme Diety, as it was stated multiple times by multiple characters (EX: Ban, Demon King). While it is true that his emotions managed to single handily destroy the arm of the DK, it was only because the DK was caught off guard and had his magic "The Ruler" turned off. So far, Meliodas has been holding back so we've never seen him go all out. Until he displays better feats against this current DK, he ties with the gods.
2. Although not explained whatsoever, Escanor seemingly recieved a buff in the recent chapters, which allowed him to deal some solid damage against the DK, including poking a hole through the DK and slashing the him across the chest. While the other characters were facing trouble defending against the DK, Escanor single handily blocks his attack with just his bare hands. Out of the characters currently fighting the DK, Escanor has the greatest feats against the current DK. This ain't even noon yet.
3. IMO, Ban is only slightly below Escanor. Based on feats, Ban hasn't been able to land a damaging blow against the current DK yet, while Escanor managed to trade blows with the DK. While it is true that we have yet to see the current escanor at full power, the same could be said about Ban. Since his arrival from purgatory, Ban's usage of his magic has been very limited, as we have yet to see Ban use magic such as hunter fest and zero hunt. Next on, Wild ties with Ban because he is most likely one of the strongest creatures in purgatory, if not the strongest. For the longest period, he fought the DK in purgatory and still managed to survive all this time. His sacrifice in order to distract the DK should be noted as a worthy feat, as Wild Full Throttle allowed him to hold off the DK long enough for Ban and Meliodas to escape. But outside of that, he didn't seem much stronger than Meliodas emotions (pre OG power) or Ban.
4. Although Mael has been disappointing in the most recent chapters, his feats should not be downplayed. Unlike Escanor, he managed to dispel true night, as well as cancel Zeldris ON with just the proximity of his presence. He managed to ONE SHOT the OG demon, something no one else up to that point was capable of doing. One of his most overlooked feat imo, is how he defeated Zeldris despite being hard countered by the DK magic. This is impressive, because Mael is seemingly more magic oriented compared to Escanor, which is why Mael had a harder time defeating Zeldris than Escanor The One did. Unfortunately, his feats against the DK possessing Meliodas's body, and his refusal to fight the current DK lands him lower than he could be.
5. Posessing one of the most broken ability in the series, Zeldris fares pretty well in this list. His ability ON is capable of practically defeating almost any characters except the users of sunshine, and the god like characters higher up in the list. His original power combined with the DK magic makes him almost unbeatable.
6. King is probably one of the hardest characters to place on this list. His feats include stomping 4C Mael, and faring incredibly well against the OG demon from a DISTANCE. He even managed to hold off Zeldris for a bit, while he was heading towards the battlefield. However, even when he arrived up close to fight Zeldris, he seemed to only tie with him. Later on, when Zeldris uses ominous nebula, King's body is seemingly being dragged towards Zeldris, which goes to show how King most likely doesn't have any counters to Zeldris's ON. In the most recent chapters, King was capable of fighting alongside Ban, Escanor, and Meliodas, and also managed to damage the DK a bit. This could be because in the past, king was low on magic when he fought the DK in meliodas body. Based on his previous feats, I would place him at #6. He would lose to everyone else above him imo.
7. The sinner is one of the most disappointing villains in the series. Even against a weakened Escanor, he is unable defeat him right away. He almost suffers a loss against King fighting from a long distance, he gets damaged and temporarily held back against a ludoshel who is disappearing, and he gets one shotted by Mael in the afternoon. For these reasons, he loses to everyone above him, and he lands this low.
8. Elizabeth has some noteworthy feats, but suffers from her lackluster engagement in battle. Among her feats include reverting monspiet and derrière back to their normal form, when not even ludoshel could do anything against them, and damaging a weaker version of DK Zeldris. Note that DK Zeldris was far from full power, and later on Elizabeth wasn’t able to do anything against the DK except heal him with ruler on. While it is true that she was once called bloody Ellie, we don’t really know what she did to receive the name. Also, Mael at one point stated that she was a worthy replacement for Meliodas (when he asked Gowther why he chose him), but based on the lack of feats offensively, she seems only powerful in her support capabilities.
9. Ludoshel is one of the strongest characters in the story, only to get overshadowed by the OP gods. Ludoshel seems capable of damaging opponents including the sinner, but falls short against zeldris who has ominous nebula, and was unable to do anything against indura monspiet and derrière. Overall, the characters above him has greater feats.
10. Finally, we have Merlin, the hardest character to place on this list. While she seems capable of out haxing most of her opponents, she seems unable to defeat characters who are the same power as Sinner or higher. This is supported by her own feats against him and her own character statements about him. Unlike ludoshel (real goddess body) who was able to damage the sinner, Merlin was completely helpless against him and believed that they lost all chance of winning. While It is true that she tricked the SD and DK, if she were to fight them head on, she wouldn’t stand a chance. In the most recent chapters, Merlin is unable to do much against the current DK.