Maxwell Lord was an egomaniac. Obsessed with bringing down the Girl of Steel should she ever prove to be a threat to the citizens of National City and the world. And in his hubris, he designed a new element replicating the metaphysical breakdown of Kara's home planet, Krypton. In other words, a synthetic brand of Kryptonite utilizing Drawf Star Alloy and various other elements not commonly found on Earth that would weaken the last daughter of Krypton twice as fast as the genuine article, which had a distinctive red hue, contrasting the natural green of real Kryptonite.
Unfortunately for him, much like Krypton itself in the weeks before its destruction, the sample was unstable and carried certain risks. But Maxwell was a man possessed, concerned only with the mission at hand, a flawless safeguard against the blonde Kryptonian.
Then, an explosion rocked his research facility in the dead of night. Maxwell Lord was one of seven people inside the facility, including security. The Sample of Red Kryptonite reached a hazardous stage in its decomposition, rapidly discharging energy until it combusted with the force of a bomb blast, expelling various forms of radiation and Dark Matter. The kind of event that could, in most cases, create a superhuman.
However, Maxwell Lord wasn't so lucky as shrapnel from the explosion ripped through his body, blasting him back against a nearby wall. Dark Matter mixed with the Dwarf Star Alloy leaked into his bloodstream, turning Maxwell Lord into a Metahuman, and by the time Alex Danvers arrived on the scene and saw the maniacal Billionaire at her feet, she knew that this was a case for the DEO and not your run-of-the-mill hospital.
---1 week later---
Maxwell Lord awoke from a short-lived coma to find himself sitting inside a strange room with a single TV on the wall. With no windows or doors to speak of.
"Hello!?!" he yelled, having his suspicions about who was behind this apparent prison he found himself trapped inside. Then, sure enough, the TV turned to static, and the visage of Alex Danvers appeared on the screen, directly addressing the Billionaire who had been seeking to hurt her adopted sibling.
"Hello Maxwell, I see you've recovered nicely. Your treatment was, at times, difficult, and we had our doubts that you would recover so quickly." Alex announced over the TV.
"Is that why you have me in this box? Is it just me, or are you scared all your nearly deceased captives will escape?" Maxwell declared, believing himself to be a prisoner. And while he was being kept here against his will, it was far from the whole truth.
"No, we issued you a psychiatric professional who recommended this setup in an effort to reduce the mental strain of your condition. The explosion caused a few metaphysical changes, and it's no longer safe for you to be around the general public. The box exists to allow you to wake up without the immediate shock of your condition." Alex explained.
"Metaphy- are you saying that I'm some kind of mutant?" Maxwell asked, looking around the room. He felt fine. And based on the bed and couch in the corner of the room. There was nothing physically wrong with him.
"Are you sure?" he asked.
"Yes, we are," Alex said, confident that something was definately wrong with the egomaniac Billionaire, aside from his 'winning' personality.
"Thanks, but I'd like to run my own tests. If it's all the same with you. Now, can you get me out of this box, Ms. Danvers," Maxwell asked, prompting Alex to turn from the screen and walk away.
"Hey, get back here. If you're going to detain me, then I get a phone call to my lawyer!" Maxwell yelled, misreading Alex's actions as a denial of his request.
Then, the walls around him began to shake as if he were at the epicenter of an Earthquake. But as the walls and ceiling began to rise above him, he realized that the truth was actually so much worse. Within seconds, he saw that he was actually at the center of a much larger room, with a bafflingly enormous Alex Danvers lifting his supposed jail cell into the air like it was made of cardboard, which to her it was.
Suddenly, the truth became clear to Maxwell as he looked up at Alex and then behind him to see an equally large Supergirl towering above him while he was somehow at the height of the two women's navels, most likely because he was sitting on top of a table.
His jaw dropped at their impossible size.
He realized that unless these two sisters had a sudden growth spurt of a few hundred feet in their early 20s, which was statistically improbable, then he must have been shrunk after the explosion. And based on the scale of Alex and Kara Danvers, he would estimate that he'd been shrunk to about one centimeter tall, as small as some species of ants.
Alex set down the cardboard cover to Maxwell Lord's room on the floor and put her hands on her hips as she addressed the shrunken Billionaire directly.
"You only have yourself to blame for this. Your physical mass has been reduced into a single space, so you're a lot tougher for your size, but it's still too dangerous for you to reenter the population of the public. Someone might not see you and before you know it, you're a puddle under someone's high heel." Alex explained.
"Did you just blame this on me?" Maxwell asked, a little insulted.
"How do I know you're not to blame for this? You probably love the fact that I'm as small as a Tic-Tac, don't you?" he asked, arguing with a woman who rivaled the size of any skyscraper in National City.
"I certainly think that it's karmic justice. You saw yourself as a big man before, trying to defend this planet against my sister, who's only ever tried to help people, only to end up like this." Alex said, gesturing to Maxwell's new size.
"Doesn't matter either way. We ran some tests and concluded that this new size is permanent. You'll be shrunk this small for the rest of your life." Alex announced, delivering the diagnosis.
"This can't be," he said under his breath.
"It is, and despite everything that you've done, I still take pity on you. Which is why I convinced Alex to agree to take alternating guardianship over you until the DEO can determine a way for you to live a normal life." Kara declared, overhearing Maxwell's statement with her Super Hearing.
"This is ridiculous! What certifies either of you to do this?" he said, his heart sinking at the thought of effectively becoming the pet to these sisters.
"I'm a secret agent working for the government, and she's Supergirl. Now shut up." Alex ordered, having listened to enough backtalk from someone she could easily pin under her thumb.
The only question left was, where were the girls planning to keep him?
1. Kara keeps Maxwell under her foot at all times, at the bottom of her red boot while she is Supergirl, and tied to the thong of her open-toed heels while she's Kara Danvers.
2. Angry with Maxwell for all the terrible things he's done trying to hurt her sister, Alex makes the suggestion that the Billionaire should 'kiss her ass', dropping him down the back of her panties for the foreseeable future.
3. Kara takes the first shift, tossing Maxwell down the front of her shirt, pressed against the front of her breast. Her options being limited by her superhero costume.