Even "going all out" all three lost and had to give up their gods though- yugi may not have tried to exploit every ability they all have, but he was the rightful keeper of the gods and used them for good instead of bringing out their fullest power for his own gain which makes him more than worthy of quite literally taking them to the grave

Out of the three, Atem arguably used Obelisk to it's fullest, especially if you include it's feats in the Yu-Gi-Oh R manga where he evolved Obelisk into The Progenitor using Divine Evolution

To be fair. Yugi didn't have a deck that supported Slifer. Kaiba's deck was built to get out big monsters so Obelisk worked at least passably well in it. And Marik jad a deck specifically made for Ra, so his would definitely work... And an extra note Marik's Slifer deck was also specifically made to optimize Slifer. Looking at it that way it makes sense that all of the god cards were wasted in his deck. It wasn't built in any way to optimize play with any of them.

He fused all three god cards during his time back in Egypt so he actually did bring their full power out

Bro anime is for entertainment. Atem summoned all 3 godcards to the field against little yugi. Yugi was just looking those god cards, we were thinking like Atem gonna destroy Yugi. But, somehow yugi managed to destroy all of them. That is how you entertain audience 😂 (epic stuff)

Atem never intended to defeat Yugi. He wanted to move on, but he also wanted to show Yugi that he was ready to go on without Atem. He wasn't duelling to win against Yugi. If he had been, he would not have allowed the God Cards to be defeated so easily. He duelled well enough to test Yugi, to have Yugi prove to himself that he didn't need Atem anymore, but he never intended to win that duel

I don't need the God cards I got the power of an Anime protagonist on my side. -YuGi probably

I don't really think he was intended to use them as weapons in a duel, but rather needed the cards only so he could put the gods to rest with him in the afterlife, as creating the cards awoke them unintentionally like how Atem was by the puzzle.

Yugi at times did even want to use the God Cards, let alone use them at their fullest.

That's how it always works. The bad guy is a total monster, brutal and powerful beyond imagining, and it takes everything the protagonist has to defeat them. Then, as soon as they join forces, the former "bad guy" suddenly gets nerfed, while the protagonist continues growing in power to face the next baddie, and the cycle continues.

Yugi: Hold multiverse universe I did use sielfer best abilites its second mouth .

Yugi took advantage of that infinite loop combo making Marik's pupet draw cards everytime that slime came back and make him lose due to not being able to draw anymore. So it backfire on Marik.

Pharaoh or Atem the real name

Yugi/Atem used the god cards because he “had” to. They are the pinnacle of DM Yugioh. Though he had a connection to other cards and his deck reflected his many connections, like those to Dark Magician and Dark Magician Girl. Those simply don’t have realistic synergy with the God Cards so he just used them for their general power instead of build a deck for them. So everything you said… correct but the reason makes sense story wise

That’s the thing though, if you notice there is a lot of times in which something would happen that took the cards out of the equation for Yugi.

I think yugiohs true card boss may have been exodia. Bad sadly he lost them on the way to duelist kingdom.

Atem didn’t use them properly

And yet he beat them all

Well tbh atem deck was more supported with dark magician, so the god cards couldn't benefit from this, the gods was more of power boost then anything else, unlike marik that supports his ra deck thats the difference

His deck was mainly for dark magician the god cards were only a bonus.