What an awesome episode, easily one of the best.
First the bad stuff:
- they really discovered Red Kryptonie awfully quick.. a "thermal" scan and suddenly they can measure radiation (once again playing it
very loose with science and technology)? How convenient.
- Maxwell Lord.. biggest flaw in the episode. Ins't Supergirl going haywire an early christmas present for him? Isn't that what he was always claiming that you can't trust aliens, especially superpowered ones? All he had to do was lean back and watch Supergirl destroy her reputation forever and maybe then come up with a Kryptonite gun to kill and be the hero, Instead he's full of remorse and even helps the DEO "cure" Supergirl. Why?
Now the awesome:
Where to begin? I loved Supergirls/Kara's progression into villain status. First the indifference, then the arrogance while fighting the escapee, the wardrobe and mentality change (well we all know Benoist is hot but damn!

) and finally her creepy, villanous state. Benoist really delivered and it was a sight to see Supergirl turn into a villain, including throwing Cat off the roof (we all knew she'd catch her because this show aint Breaking Bad but still..). Even better was her total breakdown when she normalized again, it was heartbreaking and her heart to heart with Cat was a perfect end to that storyline and the beginning of the redemption (i sincerely hope they will will milk that at the level of this episode.. it would be a shame to see 20 minutes devoted to this in the next episode and everything back to status quo).
Hank Henshaw/J'onn Jonnz, didn't expect him to blow his cover now but it was perfectly set up and executed. A brilliant moment and i loved the short fight but especially when J'onn transformed back and let himself be arrested. His scene in the prison cell and especially the small smile and wink to Alex and them saying goodbye prison style was just up there with the best scenes Supergirl had to offer yet.
All considered a brilliant episode that is a true game changer for the show that was setup long before and i hope they run with it and develop that in interesting ways that both change and elevate the show because up until now the stories are pretty mediocre and only pieces of it make me watch it (itäs superheroes, i like Benoist because she is a perfect Supergirl and is more than just hot and her supporting cast is both entertaining and fun).