My review of Luthors:
Best episode of the season (if not the series) so far. I love that they took direct influence from Smallville by giving the Luthor patriarch the first name of Lionel, making Lena Lex's paternal half-sister, and mentioning that Clark and Lex started out as best friends before things went south between them and Lex went off the deep end. It's a nice way of acknowledging some of the things that that series added to the Super-Mythos, and simultaneously adds to the overall mythos of Supergirl in some interesting ways.
I really like Mon-El as a character and think Chris Wood has been a nice addition to the main cast this season, so his interactions with Kara in this episode made me smile. I was also so hoping they were going to kiss before Mr. M (I cannot spell or say his name) so rudely interrupted them, but it should be fun to see what happens now that Kara's got another, more supernatural, suitor.
Most of Kara and Lena's early interactions were fraught with sexual tension and lesbian romantic undertones, but the show seemed to pull back from that a bit before the midseason finale, only for said tension and undertones to return in spades this episode, especially during the final scene of the episode between the two characters, which has me torn between wanting to see SuperCorp get made "series canon" and wanting to see Kara and Mon-El finally get together.
It was pretty obvious that Lillian was up to shenanigans when it came to Lena, but I still liked the interactions between the two this episode, especially since we got to see Lex's warsuit, the Persuader's Atomic Axe, and a few other "toys" on account of Lillian opening Lex's vault using Lena's DNA. It was also fun getting to see both Metallo and Cyborg Superman in the same episode and helping Lillian out, even though I do wish Hank had gotten a bit more to do. It's sad that they killed off Metallo on account of his (synthetic) Kryptonite heart exploding, but I liked the tension that having said heart be synthetic and therefore unstable and dangerous provided, especially towards the end of the episode when Kara went to go find and save Lena.
I like it when the show is able to organically create tension between our main characters because it generally leads to great character development, so the fact that they had James and Kara so openly and diametrically opposed when it comes to Lena this episode was fun and interesting for me. I also liked that they used that tension to repair the already-existing rift between the two characters resulting from Kara finding out about James' nocturnal activities as Guardian.
All in all, this was a really fun hour of television and, as noted, the best episode of Supergirl thus far this season (if not the entire series). It also set up next week's Valentine's Day episode (which, based on the preview, is giving me serious "Something Blue" [from Buffy the Vampire Slayer Season 4] vibes) really well, and I can't wait to see the full extent of shenanigans to which Mr. M gets up to with regards to trying to woo Kara.