Lisa Simpson (seasons 7-30)

Lisa Simpson is one of the main characters in the long-running American animated sitcom The Simpsons. She is the oldest daughter in the Simpsons family; older than Maggie, but still younger than Bart. She unfortunately received a lot of flanderization, even during the golden age of the show. Season 7, when her flanderization began, premiered in 1995, making her one of the earliest known cases of character flanderization in television history.

Why She Sucked
Note: This only applies to her character as depicted in seasons 7-30 of The Simpsons, as she was flanderized.
 * 1) Lisa has gone all over the place and was the quickest character to get flanderized compared to most other characters in The Simpsons (yes, even more so than Seymour Skinner) having been flanderized as early as season 7, and has also been flanderized the longest out of any other Simpsons character. She has gone from the smartest and "best-behaved" character just in contrast to Bart to a complete know-it-all Mary Sue.
 * 2) Much like Brian Griffin, she essentially became a political soapbox for the creators of the show. This is very noticeable in the 2007 movie where she nagged the town about the lake being polluted, and in "Lisa the Vegetarian", where she trashes her father's barbecue all because she is a vegetarian and doesn't like eating meat.
 * 3) She almost always acts negatively towards any kind of silliness that happens in the show, which can leave the viewing feeling bitter instead of entertained. It's okay for the writers to give her certain stances or beliefs, but her reactions should at least sometimes be funny or entertaining in some way, which doesn't seem to be the case.
 * 4) Because of her Mary Sue personality, her intelligence was dialed straight up to 11 and seems to always outclass her peers very badly.
 * 5) She is a bigot. She has had some moments of being intolerant towards others opinions like how she calls Marge dumb for believing in angels, and she holds her vegetarian beliefs against anyone who is not a vegetarian (as mentioned earlier).
 * 6) Lisa became a hardcore activist and almost an extremist, and her sardonic view became a Holier Than Thou superiority complex.
 * 7) Her nerdy interests became a patronizing enthusiasm for the most pretentious of vocations.
 * 8) Somehow, Lisa knows obscure facts that no kid her age, not even a smart one, would know or care about, such as when Texas was admitted to the Union, that Monaco has a prince, or what Occam's razor is, yet somehow she doesn't know where babies come from.
 * 9) In later seasons, Lisa eventually became the female version of Martin Prince due to her being portrayed as very uncool and lots most of the friends she had in earlier seasons.
 * 10) She is at her absolute worst in episodes like "Bart vs. Itchy & Scratchy" and "On a Clear Day I Can't See My Sister".
 * 11) *In "Bart vs. Itchy & Scratchy", she publicly humiliates Bart after he laughs on a gag of a Itchy & Scratchy girl reboot by publishing the stream that Bart was in onto the internet, resulting in Bart getting beaten up at school.
 * 12) *"On a Clear Day I Can't See My Sister" sped up her flanderization and it ultimately completely ruined her as a character all together, due to her acting extremely unlikable towards Bart by getting a restraining order towards him because Bart insulted Judge Harm's husband which forces him to live in the backyard and even abuses her power with the restraining order by constantly poking Bart with a crafted 20 foot stick that has a screwdriver attached at the end. In addition, she was made to be a HUGE karma houdini as she never gets her comeuppance for her cruel acts.
 * 13) In almost every single episode that involves her being in a conflict with something, she's always portrayed like she's in the right of the conflict, always comes out on top, and they are always at a desperate attempt to make you root for Lisa. Like in any episode where Bart is superior to Lisa at something, and the episode tries to paint Lisa as sympathetic despite that she's just being jealous of Bart, which is a petty reason to make her sympathetic.
 * 14) She is shown to be willing to abandon her family in pursuit of glory.
 * 15) * In "Elementary School Musical", she ran away to pursue a career in performing arts.
 * 16) * In "MyPods and Boomsticks", she goes to the Mapple HQ without telling her family or ask them about the bill problem from it.
 * 17) * In "Lost Verizon" (the episode that started this trend), she wastes all her family time to go to Peru despite the GPS chip being part of the bird and the family searching for Bart.
 * 18) She's always butting into people's business and trying to force her opinions onto people when they don't ask for them or want them, basically making her as Ned Flanders calls her "Springfield's answer to a question no one asked".
 * 19) Even when she isn't being unlikable or political, she can be treated like a butt-monkey at times as well, such as in "My Sister, My Sitter", "Lisa Goes Gaga" and "Bye Bye Nerdie".
 * 20) She is extremely hypocritical, or self-serving in a lot of her causes. One infamous case being her motives for joining the school football team, becoming upset when there were already four girls on the team.
 * 21) Two of her infamous quotes:
 * 22) *"You shouldn't be part of a protest if you don't care about the cause."
 * 23) *"Well, Bart, how does it feel to be trolled, memed, gif'd, and dare I say... pwned?"
 * 24) She cannot bare anyone else to be the center of attention. For example, in "Jazzy and the Pussycats", she became jealous of Bart getting attention for his drumming talents. Going as far as to claim she deserved attention and not Bart as she was more important.

Redeeming Qualities

 * 1) She was a much better character in the first six seasons and has massively redeemed herself since season 31.
 * 2) *She even mocked SJWs in the season 32 episode "Wad Goals".
 * 3) For the most part, she can still be a likable and funny character due to the fact that she is still a Hollywood Walk of Fame character like Ms. Piggy, even in the old and new seasons.
 * 4) *She can be likable in a few episodes like "Lisa's Date with Density", "HOMЯ", "The President Wore Pearls", "Lisa's Sax", "My Sister, My Sitter" (despite being treated like a butt-monkey), "Smart and Smarter", etc.
 * 5) *Similar to her father Homer and and her older brother Bart, there are still episodes where she is at her best.
 * 6) In "The Man Who Grew Too Much", it's shown that she's for GMO, something that SJWs would attack, meaning that she's not always alt-left and she can give new science a chance, despite her flanderization.
 * 7) Yeardley Smith still does a good job voicing her.

Trivia

 * Lisa mainly received mixed-to-negative by fans of The Simpsons, mainly due to her becoming a bland Mary Sue and a political soapbox for the creators. Some fans even go as far to say that she is the worst character in the entire series. However, there some fans who still like her (mainly before the season 16 episode "On a Clear Day I Can't See My Sister"). Semi-long running social media Mew Mew PeachySilver New AKA sonicandmlplegnd99 also hates this character quite a lot.