At present some of the dead giveaways are hands, fingers (number/angles), feet, eyes, any text, objects merging/blurring together, guns, noise/debris, and things that should be straight lines. Some of this stuff might be attributed to the artist making a choice, but most of it is too obvious to be an intentional artistic choice. That said, I've seen "AI" art that is better than what some publishers put out. Hands are hard to draw right, even for people. I'd take most "AI" art over anything from Rob Liefeld, for example.
The more the art tries to depict things we're familiar with, the more obvious it will be that it's "AI" art. The uncanny valley. We know what it's supposed to look like, but it's wrong. The more details the art includes, the more likely the "AI" is to get something wrong. Once you prompt the thing to not depict humans, human-like creatures, or objects we're familiar with...or to use a simpler, more abstract art style, things get a lot harder to spot.
Another dead giveaway is consistency over time. Even with an incredibly detailed prompt, the thing won't produce similar results over time. All three of the Hulk images are from the same prompt. It's like three different artists drew those. Having the same character, with the same details, appear in different situations is basically impossible.
Here are some examples.
Too many fingers.
The feet.
The feet.
The text on the jerseys. The pucks and sticks are clearly wrong. All beyond "artistic choice" as an excuse.
But this one...
I don't immediately see anything that couldn't be attributed to "artistic choice."