There's a small subgenre in Superhero comics that details the final adventures of various superheroes, the final point of their life. See for example Marvel's 'The End' line for the largest example. But out of all the stories in that vein, Alan Moore's 'Whatever Happened To The Man Of Tomorrow?' is easily the best of the bunch. The final adventure of Superman... well, the Silver Age version at least.
It's really the best way to wrap up the saga of such a larger than life character- detailing his last battle against his greatest foes, showing the defeat and destruction of his rogues gallery to wrap up those loose ends, and even wrapping up the details of his personal life. It takes Superman into the most brutal and grueling battle of his career, the strongest challenge he could possibly endure, and despite all the death and destruction wrought in the story it ends on a high note to show that Superman has earned his happy ending despite the strife.
Curt Swan's artwork fits in perfectly, the de facto artist for classical Superman penning his final adventure, packing so much detail and beauty into each panel and giving it a real silver age aesthetic. Make no mistake though, this story does get shockingly dark at times, from body horror to family unfriendly deaths... but what else would you expect from the guy who deconstructed Superheroes just to rebuild them again?
Definitely worth a read, a real classic for the Man of Steel.