My favourite 'Cosmic' stories were the 'classic' Ditko run on Dr. Strange. Magical. Moody. Surreal. 'Cosmic.' *(Especially the moment Dr. Strange meets Eternity for the first time.)
Even more so if you read them in black and white (which I did with the Marvel UK reprints...)
Recommended reading.
As for 'Secret Wars.' *shudders. I remember this like it was yesterday. A brash, shoddy and cheaply drawn crossover. Whither subtlety..? That's what I thought at the time. Cheap and tacky. And yes, Beyonder. He certainly was... Many, many years later I watched the Power Rangers and after a 'rash' of 'getting hooked' on it...I've had my therapy and now I'm fine.
At least DC had Crisis...oh wait...*
Pre-Crisis. I do remember one story, vaguely, where Superman tries to pierce the ultimate barrier. But Spectre is the one he finds just before he gets 'there.' Naturally, Superman tries to get past the Spectre but is humbled in short order as the Spectre politely reminds him that he is going no further...and that some things are beyond (no pun intended...) even Superman's powers...
I do like the Silver Age Green Lantern stories. Gil Kane's elegant line work and sound composition with reasonable dose of Cosmic.
Or Kirby's Thor. A viking longboat that 'flies' through space? Got to love that...
Or what about the seminal introduction of 'the power cosmic' Silver Surfer in the Fantastic Four? The squaring up of Galactus to noble Watcher? John Buscema's art chores on the Surfer series that followed later. Svelte space opera.
Azrael.
At a few thousand for the entire galaxy, the writers proved they have no idea how large space is. At 3600 sectors for the entire universe and two per sector, the writers proved they were insane. Each pair of Green Lanterns are patrolling a cubic gigalightyear per? That's even more ridiculous than hiring one lifeguard for all the beaches on Earth.
Think of all of the beings on the millions of inhabited worlds in billions of galaxies in each sector of space. Of all of the trillions of problems that happen every second in that space, the Green Lanterns get to work on one, maybe two. The idea that only one is important enough for the Green Lanterns to work on at any one time is statistically impossible. Random chance says that there have to be thousands of years when nothing important enough happens, and then a million separate cosmic problems happen on the same day. You can't have one a week happening unless Evil schedules ahead.
How do the Green Lanterns get out of bed each day, eh? *Sweeps post into the nitpicking bin.*
https://www.youtube.com/watch?v=8WZ0XSf23rsPPS. Let's hope we never find out.
https://m.youtube.com/watch?v=kbcoOqGKFi8
No stupider than that?