Warning: spoilers ahead for Episode 4 of Supergirl Season 3, "The Faithful."
Supergirl is going in a brand new direction with the new supervillain of Season 3. We've known for a while that the DC Comics baddie by the name of Reign was going to be Kara's new nemesis for the third season, but Supergirl is taking its time in transforming single mom Samantha into the genetically engineered weapon from the planet Krypton. We're watching Reign's origin story in Season 3, and "The Faithful" gave us our first big clue that Reign could be Kara's most dangerous supervillain to date.
For the majority of "The Faithful," the most dramatic story surrounding Samantha was her struggle to balance her work with the needs of her daughter. It wasn't until the very end that we got another big indication that she's much more than a single mom with a stressful job. She was standing in her bathroom and fiddling around in her medicine cabinet until she got a look at herself in the mirror, and she saw her skin covered in bizarre symbols. She also saw a mysterious figure in the corner who seemed to come out of nowhere. Then Ruby came in, and from her point of view we could see that there were no marks on Samantha's skin and there was no other person in the bathroom. Samantha was understandably terrified and panicked.
Of course, being frightened and frantic doesn't make a person into a murderous villain, and Samantha's breakdown at the end won't be enough for her to go full Reign on Kara and Co. The fact that Ruby couldn't see either the symbols or the person indicates that Samantha's genetic engineering as a weapon may be activating in some way. Her powers as a living weapon engineered by Kryptonian scientists who are probably long dead combined with her ignorance of her own origin could be that she'll be dangerously unpredictable.
Assuming Samantha maintains her love for Ruby even after she goes full Reign, she could be a wild card for the good guys and the bad guys of Supergirl. Even when she has had to prioritize work over spending time with her daughter, Ruby has been Samantha's top priority. If Samantha continues to prioritize Ruby even as she becomes more powerful, she could be dangerous to anybody and everybody in her path.
We'll have to wait and see. Despite how Supergirl seems to be activating Samantha into Reign, Lena Luthor is still arguably the character who could do the most damage to Kara and Co. if she so chose. The difference between a potentially evil Lena and a potentially evil Reign is that Lena is somebody who likes to have control. Samantha's transformation into Reign may not allow for much control. Only time will tell. If last week's episode really was a clue that the timeline has been changed, we may not be able to take anything for granted. The one thing we can say for sure is that Reign will look pretty badass when she finally debuts in all her villainous glory, thanks to the first look that was just released.