Superheroes can't be all-powerful because all the drama in their stories comes from them overcoming the odds. One way creators can work around extra-strong heroes is by nerfing them, essentially weakening them, whether by injuring them, introducing a magical force that strips them of their power, or providing major obstacles. James Gunn's DC Studios has already used this tactic a few times since kicking off the DCU with Superman, including with a recently introduced hero with plenty of potential.
DC Studios made the controversial decision to cast an older actor as Hal Jordan in Lanterns. Fans were disappointed that they probably wouldn't get to see their favorite Green Lantern at full power in the DCU. But they remained cautiously optimistic that Lanterns would let Kyle Chandler's Emerald Knight loose a few times. The final product didn't deliver, leaving its titular heroes between a green rock and a hard place.
In nearly every scene where Hal used his power ring, it was low on battery, so he couldn't go all out and had to conserve power. Even when his battery wasn't far away, he would go long stretches without charging, giving his enemies the upper hand. It also wasn't hard for people to take the ring off Hal's hand; William Macon's forces and John Stewart did it without much of a fight, leaving Hal powerless and at the mercy of his captors.
John will surely be better about power ring maintenance now that he's the Earth's Green Lantern, one of the many lessons he learned as Hal's protege in Lanterns. However, just because one DCU hero is no longer nerfed, that doesn't mean they're all firing on all cylinders. James Gunn has ensured that a decent chunk of DC Studios' good guys always fight an uphill battle when they step on screen.
Every Major Hero James Gunn's DC Studios Has Nerfed
Superman
When James Gunn took over DC Studios, he immediately decided his version of Superman wouldn't be all-powerful. He doesn't find that kind of character interesting and believes their existence makes it harder to believe small-time heroes could exist and thrive.
Gunn put his money where his mouth was in Superman, which kicked off with the Man of Steel losing his first-ever battle to the Hammer of Boravia. David Corenswet's character took a number of beatings in his big-screen debut before outsmarting his opponents and saving not only Metropolis but the world. While Superman may come back stronger in Man of Tomorrow, don't bet on him simply overpowering Brainiac and his robot army.
Supergirl
In many DC Comics runs, Supergirl has the strength advantage over her cousin because she's never practiced holding back her powers. Clark Kent spent so long on Earth trying not to break things that he adopted a reserved fighting style. The conflicting philosophies can sometimes drive a wedge between the two Kryptonians.
While the DCU certainly puts Supergirl and Superman at odds at times, it's more about Kara Zor-El's partying habits than anything to do with her power. Like her cousin, Supergirl lost her fair share of fights in her solo movie. And she got bested by opponents far weaker than Ultraman. As it stands, Supergirl's nerfing keeps her out of Superman's league.
Hawkgirl
Superman introduced the Justice Gang, a superhero team Maxwell Lord funded to keep Earth safe from major threats. Lord's youngest recruit was Kendra Saunders, aka Hawkgirl. James Gunn's movie revealed little about her character, except that she isn't afraid to stand up to anyone.
Despite giving Hawkgirl some memorable action sequences, including one where she went to town on Boravian soldiers and killed President Vasil Ghurkos, it still felt like Superman nerfed Hawkgirl. That's probably because it didn't mention Nth metal, a special substance that makes her a powerhouse in the comics. There's no doubt that the DCU's Hawkgirl is strong, but she doesn't hold a candle to her comic book counterpart, who has access to plenty of Nth-based items.
Metamorpho
It's hard to imagine Metamorpho being stronger than he already is. In Superman, he could change his molecular structure at will, which allowed him to create Kryptonite and keep the titular hero at bay. And when he realized the Man of Steel was on his side, he made a yellow sun that recharged him.
There's one important aspect of Metamorpho that Superman didn't address, though. The comic book version of Metamorpho is immortal; while he can be hurt and even killed, his abilities allow him to return. If the DCU's Metamorpho had that trick in his back pocket, he probably would've gone after his son much earlier.
