Which space marine chapter best follow his original ideals?

That humanity has to be united under one banner and that technological advancement and conquest are its destiny. And also to not kill other members of your species for no fucking reason

As much as it pains me to say, the Ultramarines probably follow the imperial truth the closest if you are talking about 1st founding chapters.

Salamanders would probably be second.

Angry Marines.

...

In no particular order: Space Wolves, who had clashes with the inquisition for mind wiping people on Armageddon and shit. They're big on defending civilians.

Salamanders: Bro tier. Always try to save civilians, are even expected to live normal lives as well with regular people when not fighting/training.

Lamenters: will literally destroy themselves to save people and go out of their way to protect the helpless.

Other than that, I don't see a lot of them really being all that close. Not even the Ultramarines. Maybe with Roboute back it's different, but before that Ultramarines didn't even follow the spirit of what Guilliman's tactical book said or the whole "space marine chapters that split off are supposed to do their own thing" that Roboute wrote because successor chapters basically all stayed on top of each other and may as well have been a legion. I think they had good intentions, but they fucked up a lot of shit and don't fit that closely with the Emperor's vision.

But, as said, with Roboute back they now have a primarch who was actually alive and spoke to the Emperor so I'm sure he'll clean house.

The ultramarines should be hated when they're represented as "da best of da best spiritual liege" and all that. What they should be seen as is empire builders and that should be their legions special ability. That they go to a world, fight it out and then set up solid infrastructure. They take losses along the way but they have numbers brought about by so many recruiting worlds and good tactical and strategic knowhow rather than direct combat skill

Or the Inquisition, or church (forge the name), will try and gag him because he is a direct threat to their power. This may very well lead to their undoing or another civil war as they cling to power because I have no doubt most if not all SM would side with blue boy.

>or church (forge the name), will try and gag him because he is a direct threat to their power

I thought Guilliman was keeping quiet on the whole "the Emperor hated religion, actually" stuff to ensure that that didn't happen?

You have multiple containment threads - STAY IN THEM.

He is. But I doubt anyone would have the balls to fight him anyway. Especially not since custodes would also side with him, and they'd take out anyone they want given they already infiltrate everything on Terra. When you see primarchs, space marines, and custodes against you, you kinda have to stop and wonder who knows better.