What's next, Joker wearing black and Batman wearing purple?
The New 52 version of Lex Luthor was an amoral egotist, but not really a villain - like, he distrusted Superman (he basically thought all Supes' good deeds were just "virtue signalling" - aka, doing the right thing not because it's the right thing to do, but so people can see you doing it) and he did commit crimes (perhaps a little light treason), but he wasn't swearing vengeance or building doomsday
rays to hold Metropolis ransom or anything. When the Crime Syndicate invaded the main DCU reality, Lex rallied all "our" supervillains to help fight them off, which eventually led to him being invited to join the Justice League.
As the League went up against Darkseid, Lex found himself on Apokalips, where he took advantage of a local prophecy to be declared the new Lord of Apokalips (complete with all the powers that entails). To honor their new savior, the residents of Apokalips crafted him a new suit of armor. He had no interest in ruling another planet (he's like a white nationalist, but with Earth as a whole instead of just the random square foot of dirt where his mom plopped him out), so he came back home and decided to be the new Superman (since the existing Superman had recently died) - after all, if he really was capable of helping people, why not do it? And soak up some of that glory Superman had been hoarding for himself?
"Rebirth" Lex Luthor is the build-a-figure for the sixth go-round of Mattel's DC Multiverse line - originally intended to be split among five figures, that number was eventually dropped to four and
the parts distribution was rejiggered. Like, Vixen was originally just going to come with the cape; instead, she has the torso. The cape now comes with Batman, as does the head; he was originally just going to come with a single leg. Both legs are now with Wonder Woman, when she was first planned to only have one of them. Ray, meanwhile, has the arms, which was always the plan, so at least one thing about that figure made it all the way through without getting changed!
Since Lex was genuinely trying to be a hero when he was wearing this suit, the face may not be what you normally think of for him: he's not frowning, he's not scowling, he's not angry, he's not haughty, he's... actually got a bit of a smile? Just tugging at the corners of his mouth a little, like it's something he's unaccustomed to. It works for him.
The armor is quite stylish. It's made from Apokaliptan tech,
though it manages to look heroic and not sinister. It's a lot of shaped panels worn over a bodysuit beneath, with thicker armor over the shins, forearms, and shoulders. There's a Superman symbol on the chest, and a matching shape on the waist. The cape he wears is really Superman's: Kal-El bequeathed it to the Daily Planet, who had it on display in their lobby; Lex bought the entire business just so he'd own the cape, and be able to wear it himself (though honestly, the toy looks wonderful even without it on, so it's good you have the option).
Befitting a fill-in Superman, the armor is blue with a few red accents. But to set it apart from the real guy, it drops the yellow
and adds in silver, matching the color of his S-shield with some insets on the ribs, and pods on the waist and hips. Then on top of all that you've got his pale pink skin sticking out and drawing attention to just who is wearing this suit. The dark grey undersuit isn't just flat, it's got various textures to keep it interesting next to all the fun and fancy armor panels.
Lex's articulation is top notch. He has swivel/hinge ankles,
double-hinged knees, swivel thighs, balljointed hips, swivel waist, hinged torso, swivel/hinge wrists, hinged elbows, swivel biceps, swivel/hinge shoulders, hinged neck, and balljointed head. We will forever remember Mattel as the company that took a decade and a half to give characters who can fly the ability to look up. Seriously: a hinge in the neck and a balljointed head. Hasbro figured that out in 2009, and in the year of our goddesses 2020, it remains the best option action figures have. So naturally, Matty ignored it until the last minute.
Build-A-Figures don't generally include accessories.
The cape would probably count here, since he does sometimes appear without it, but if you get the two Walmart exclusive figures (which shipped months and months sooner than the actual series), you get a few extras. Based on a scene in Action Comics #967 showing one character's interpretation of the future, the extras are a Mother Box and an alternate head, featuring Lex with a visage more similar to Darkseid himself.
Lex Luthor being Superman is a strange concept to wrap your head around, but it makes sense in context, and the story makes clear that Lex really does want to be a "good" guy, for his own reasons. The toy is impressive, both in design and execution; if Mattel had been giving us things like this all along, they might not have lost the license to Spinmasters and McFarlane.
Vixen | Gotham by Gaslight Batman | The Ray | "Rebirth" Wonder Woman
Spoiler | Harley Quinn