This is technically a two for one hero spotlight. I'm not gonna just do one on Superman, what can I really say there that hasn't been said a hundred times? But one of my favorite times in Superman comics was the energy era Superman, especially when he was split into two. Lots of people hated it, but I loved it and I'm fully prepared to defend my position.
First some background. Back in the 90's at one point Superman had lost his powers. In an attempt to regain them using some tech from STAR Labs or something he accidentally got turned into an energy being. Unable to hold himself together STAR Labs gave him a containment suit that would become the electric blue suit we see on the left there. Superman now had a completely different set of powers he had to learn. He could still fly but he also had various energy manipulation powers, he could become intangible, absorb energy, shoot bolts of energy, etc. But he really had no experience using these powers, at one point he actually had to take pointers from a teenage super hero called the Ray. And what was most interesting to me when he turned back into Clark Kent he was completely powerless, so he still had to deal with being vulnerable in ways he wasn't used to. He had to deal with everyday human things like paper cuts and bruises in his Clark Kent life.
Then things got weirder. Superman was battling the evil Cyborg Superman, then just called Cyborg, and he used some sort of prism energy splitter thingie in an attempt to rip Superman apart, and in a nod to a very goofy silver age story, he split Superman into two energy beings, one red and one blue. Although there were slight personality differences, Blue being calmer and more analytical, Red being more emotional and hotheaded, there were both equally Superman, equally Clark. There wasn't a 'real one' and a 'copy'.
Various hi jinks occurred both as Supermen and as Clark (obviously they couldn't let anyone see two Clarks together) for a little while. At one point Lois even left to go live with I think her sister because she couldn't take having two husbands. Kind of a selfish bitch move if you ask me. It was hard on the Clarks to go through this and I'm sure they could have used their wife's support. But then Lois has always been a bit of a cunt, frankly I think Superman can do better. Eventually during a big battle against the Millennium Giants the two energy Supermen were seemingly destroyed stopping them. But then a reborn Clark showed up with the memory of both Supermen and after a little time in the sun he got his normal powers back.
You know what you can shit on this saga, era, story, whatever you want to call it all you want but I thought it was awesome. Superman, the king of super heroes, the untouchable never can lose hero can get pretty fucking boring. But now he had to learn a whole different set of powers and deal with juggling two people leading one life. The moment that struck me in this era was at one point Superman was fighting someone who tried to shoot him, Supes went intangible and the bullet passed through him and hit Lex Luthor's wife or girlfriend (I forget which she was) and Lex said to him "What good are two Supermen if they can't even stop bullets?" While Superman did get that woman to the hospital and I think she recovered the question haunted him, his lack of expertise in his new power set haunted him. Superman actually had to try for once. He/they actually had to deal with fatigue, hunger, injuries as Clark and as Supermen they had to deal with learning all over again how to be a hero to the point of asking a teenage hero for advise. No it couldn't have been a permanent change, but for a little chapter in the characters life I for one think it was a pretty damn interesting one.