Okay i will give my points one by one.
Note i will refer to your images by giving No.1,No.2 as in the order you posted for our convenience.
Fair enough. I don't think we'll 100% agree here, so I'll be giving my last counter-arguments on this to prevent the thread from going off-topic. You make good points though.
First of all we know Slaying advantages allow you to cover huge gap in powerlevels and even gain you a victory.
That is why Dragon Slayers in GMG managed to fight Dragons even though stronger mages like Jura failed.
I somewhat agree and disagree with this. In my opinion, slayer advantages only come into play when we're talking about damage (attack power). It shouldn't really affect defense or anything else. That is more like resistance which is only related to elements (elemental resistance).
So for the dragon slayers during the GMG, I would agree that their attacks on the dragons were more effective than someone like Jura. However, if the dragons were to swipe Jura away with one hand, I would think that the dragon slayers would share the same fate. Actually, I can see Jura tanking it better (although some may disagree).
Now coming to Gray's Des Magic i will analyse his performance
Against Tempesta
Who was either weaker or same level as Gray
Gray one shotted him
Against Mard Geer
Mard Geer was stronger than him at that time.
He destroyed him in his Base state and used one hit to finish him in his EF though DF Natsu also weakened him.
Now if i go by your logic that Des Gray was =Partial END then it would not have been a match because Gray would have one shotted him with his Des Magic.
But that didn't happen even though partial END was hit by Des Magic many times.
This itself proves that Partial END was much stronger than Gray.
So using the logic I just described above, then it would make sense for Tempesta to be one-shotted by Gray. But lets just say Gray decided to tank Tempesta's attack. Would he come out with minor injuries? I don't think so.
Now did DeS Gray get a boost in defense? Yes. That mainly came from the fact that Silver transferred his MP to Gray. But is this the result of having slayer advantage? Again, I don't think so.
Mard Geer is the same way. Gray struggled to compete with Mard Geer in virtually every stat including defense, speed, MP, etc. The only advantage he had was attack power. That is why all he needed was a distraction (Natsu) so that he could land a hit and defeat Mard Geer.
Now coming to your images.
No.1 image
I will not disagree there Gray and Natsu's punch was same and created a nuke.
No.2 image
Now here i will say even though the punch appear to be same but power was definetly on Partial END's side.
Gray's expression itself betrays that he is feeling the pressure.
I don't know about Gray's expression. You might be right, although I think part of it is just because Gray was angry.
Now the images you put under the Spoiler thread,"Gray's defense"
No.1 image
If you look at image closely where Natsu was thinking about Lucy Partial END did not attack Gray himself.He destroyed Gray's magic.Because in the next panel of Gray you see small small particles of ice flying in the air which was destroyed.
(though i may be wrong here)
No. 2 image
Here Natsu punched Gray but he didn't attack him with fire attacks.Now we can't judge a person by his punch only.Mard Geer fought Sting and Rogue in a physical fight for much long but he didn't take them down completely.So we can't say Mard Geer<Twin Dragons.And Natsu's performance was better than Mard in this respect.
Now the images you put under "Gray's durability"
No. 1 image
This is the tricky part for me.Natsu used a Fire Roar which hit those spiky ice structures which Gray created and destroyed it.It didn't directly hit Gray as far as i see.And Natsu launched him directly at ice wall but he couldn't reach Gray.
Yeah, now that you pointed it out, I think you're right about the first image. Natsu broke Gray's ice. He didn't actually come in contact with Gray himself.
For the second image, I can't tell whether Gray was hit. I assume he was because of the force pushing him back but then there is ice in the background so he might have used some sort of shield. I'll leave this up in the air for now.
For the roar though, I believe Gray was actually hit because we see Gray scream at the bottom panel of the first page. Also, the page after that, you can see smoke coming from Gray himself. But I can be wrong.
Now some bonus points.
We all know Natsu and Gray were potrayed as equals.And we saw Brandish's magic working on Natsu.So we can assume it will also work on Gray.But Natsu as END with partial power became so strong that her magic didn't work on him.In the CR Translation she says,"It is far stronger than me".And also Dimaria saying Partial END's power surpassing Chronos's and being able to move within the Age Seal.
Here is the problem that I have with the idea of slayer advantage. I honestly think people put too much emphasis on it. This "slayer advantage" was originally supposed to be more like a boost. I never saw it as something that would turn a fight 180 degrees.
We saw how Chelia did against Dimaria despite being a god slayer. It wasn't until she gained an immense power boost (Third Origin), that her slayer advantage helped her win the fight. Before that, she still had slayer advantage, but she was too weak to do anything.
So if Gray can compete against E.N.D, that means he is close to his power. If you want to say E.N.D is stronger than DeS Gray, I will let it slide. But I still think Gray is
at least comparable. And by that, I mean Gray isn't too far behind.
Cant really scale Gray's durability to ENDs attack power because Demon Slaying magic absorbs demonic attacks
I don't think it does. If you're talking about
Momento Mori, that was a one-time deal which happened due to the nature of the attack. Mard Geer's thorns which are still powered by curses still affected Gray.