The one thing I want is for people not to listen to the damn fans who love one character, but hate another.
Make the characters who they are. Don't cause conflict where there doesn't need to be, don't bastardize the characters because you need them to be dark and edgier because you think people will relate to it more.
Don't make Superman a dick because some people don't like superman. It won't endear those people to Superman, and you'll piss off the fans of Supes. If people don't like superman, THEY DON'T HAVE TO. They have Batman. They have the Flash. They have Wonder Woman.
Do not pull a fucking X-men. Do not make one character the focus and leave the fans of the others to rot. If you don't like Wolverine, the X-men movies aren't for you. They changed Storm to be a docile exposition version of herself to serve as Wolverine's and the audience's guide. They changed Jean Grey to just be someone to lust after. Cyclops never had a chance. I got two seconds of my boy Colossus in the first movie. It was a disappointment if you didn't love Wolverine.
Pull an Avengers. They didn't make Cap Edgy because his morals are outdated... They made him hold them up and say 'This is what I believe in. This is what the Character is. Even if the world is now different, this character still embodies a different world.' That's what makes him interesting nowdays.
Superman IS a boyscout in a world where Evil is lauded, being an ass is the only way you can show intelligence, and Posturing is how we interact with each other. Superman doesn't belong in this world in so many different ways. Use. That. Don't fuck it up just because there's people who don't like superman.
Same for Wonder Woman.
Same for Batman.
Same for every character that someone is a fan of, yet someone else isn't. Those Flash fans are going to pay to see the Flash they love, not the Flash that script writers think they need to punch up to make more relate-able.