When a series has a main character as powerful as Supergirl, it can be difficult to come up with credible threats. The more things escalate, the more ridiculous they become. Part of the appeal of a show like Supergirl is the campy embracement of the superhero genre and all its associated flaws.
Grand stories require grand leaps in logic. The superhero genre in general requires a greater suspension of disbelief than most just in their basic premises, so any further plot holes seem even more ridiculous. That's part of the fun!
10 Gotta Start With A Classic
Everyone likes to ridicule the idea that nobody would recognize the Supers due to a simple pair of glasses. Newer superheroes and villains put a lot more effort into concealing their identities, from domino masks like Dreamer's to full-face coverings like Agent Liberty's. That being said, there are some experiments that results lend credence to the idea. There is a known psychological effect called "change blindness," where people will miss large changes in their surroundings as long as their line of vision is momentarily broken.
Daniel J. Simons and Daniel T. Levin conducted an experiment on change blindness where they started conversations with the test subjects and then distracted the subjects and switched out the person they were talking to. Only half the subjects even noticed that they were talking to a different person. Maybe those people who think they'd catch on right away are giving themselves a little too much credit.
9 Fans Are Frustrated With Kara's Love Life
Kara spent the entirety of season one pining for James and they finally got together in the season finale. Then in the first episode of season two, they agreed that they weren't really feeling it after all, most likely due to the decision to add Mon-El to the show as her love interest. The way she dropped James just to get together with Mon-El, who was a terrible person when they met, was unsatisfying. She spent so much time trying to "fix" him and when he eventually did become a better person they wrote him off the show.
Of course, Mon-El came back for a few episodes in season three just to break her heart again by revealing that he was married. Now they've introduced William Dey, an original character, who is pretty much the blandest, most pointless addition ever. The actor's doing his best, but the character is so generic it's painful.
8 Very, Very Frustrated
The level of priority given Kara's dating life is ridiculous. She's a superhero. Less kissing, more punching please! Season four gave fans hope that the show would stop trying to shoehorn in a romance when it wasn't the right time. Then they added William.
Even worse, he's clearly written to be Kara's perfect match. He's a fellow reporter, volunteers at a soup kitchen, makes obscene amounts of baked goods, harmonizes with Kara during karaoke (they have the same favorite song, of course), and just so happens to be suspicious of Lex Luthor. He's so perfect for her that it's actually nauseating. Just let the woman be single!
7 Family Bonding
It's no secret that the Luthor family is messed up. They're all brilliant, emotionally stunted, and prone to insanity. Lillian is the one who's mostly got everything under control, but even she is at a loss when it comes to some of Lex's schemes. In season four she tried to poison him. In season five she helped him manipulate Lena. In season six she slapped him when he threatened Lena.
Lena, meanwhile, is trying to be a good guy—her success is debatable—and has finally realized that nothing good comes from working with Lex. The final nail in the coffin of their brother/sister relationship was the punch she threw while he was still mid-monologue. She may be trying to distance herself from the family, but one thing Lena and Lillian have in common is that they're done putting up with Lex's nonsense.
6 It's Time To Seek Help
Brainy and Lena are two of the smartest characters in the entire Arrowverse, but they have issues when it comes to dealing with emotions. When Brainy was panicking after Agent Liberty seeded the atmosphere with kryptonite, Lena told him to put his emotions into little boxes, which is not very good advice.
Neither of them were successful at balancing their intelligence and their feelings and Lex used that to his advantage in order to manipulate both of them into working with him. While they're back on the right side now, they clearly need to sort some stuff out. Considering that Kelly Olsen is pretty much a supertherapist, it's surprising that she hasn't sat them both down and made them talk it out yet.
5 This Is Fine
One of the main themes of season 5 was where to draw the line between technology and real life, but the Obsidian lenses took things ridiculously far. When people started to use them in public, losing awareness of their surroundings, they became a concern. The more the technology advanced, the more lifelike that artificial reality became, with more and more people losing themselves in it.
Still, when Lex Luthor arranged for the Sun Eater to escape the Fortress of Solitude and it attempted to, predictably, eat the sun, people put in their Obsidian lenses and switched over to the virtual world rather than dealing with the disaster at hand. Despite the fact that everything ended up alright, watching everyone stop whatever they were doing and put in their lenses was as sad as it was comical.
4 Lena Loves To Keep Us On Our Toes
When Lena Luthor was introduced at the beginning of season two, fans were split over whether she'd turn out to be good or evil. Most were happy with the revelation that she was indeed on the side of the Superfriends. Over the next few seasons, Lena's morally grey approach to their problems complimented Kara's somewhat naïve idealism, and the combination of a Kryptonian and a Luthor was potent.
When Lena found out that Kara was Supergirl, she went through a downward spiral that not only sent her character back to square one but further as she embraced the Luthor within her. Her character can be frustrating, but Katie McGrath portrays her so honestly that it's hard to stay mad.
3 Sincerity Is Worth Nothing To A Luthor
The Luthors are an incredibly messed up family. Seeing as how the family is predominantly comprised of supervillains, they're not exactly great with their emotions.
It's hard to fault Lena for being suspicious, emotionally stunted, and unforgiving considering her upbringing, but Kara's about as earnest as a golden retriever puppy and just as hard to be mean to. Watching Lena channel her inner villain towards the one person who's been consistently kind to her with no agenda is maddening.
2 Lena. CHILL.
Lena's a popular character even when she heads down a dark path, which she's done multiple times. She experimented on Reign in secret, manufactured kryptonite, and worked alongside Lex without telling anybody. Her worst turn on the dark side happened in season five.
She's always believed that the ends justify the means— a philosophy not shared by the Superfriends— but she completely goes overboard when she begins Project Non Nocere. In her eyes, she really is doing a good thing, but from the outside, it's clear that she needs a nice vacation.
1 Remember Clark?
When Supergirl was in trouble in past seasons, Superman didn't come to her aid because he was on Argo with Lois. When the CW decided to make Superman & Lois, the two of them moved to Earth, meaning Clark should be there to bail out his cousin in her time of need.
If Superman & Lois was mainly a superhero show, it would make sense that he'd be too busy to assist Kara, but it's a drama centered around family relationships. It's pretty ridiculous watching Kara get beaten down by a superpowered Lex Luthor and knowing that Clark is only a few minutes of flight away playing assistant coach at his kids' school.