I want to hear about the pokemon line you wish ended with the middle evolution.
I want to hear the reasons you think the middle is the peak pokemon in the evolution.
I want to hear it all. For example, my beautiful, perfect evolved Swinub becomes a masterpiece -
Piloswine:
Mamoswine who???
And an honorable mention goes to this ideal specimen -
Lairon:
My Lairon will forever hold an everstone so it doesn’t become a two legged metal BEAST.
Thank you for coming to my TED Talk.
Gengar could have been a separate Pokemon.
Rhyperior is disgusting.
Magmortar is cool in theory, but ultimately unnecessary.
I prefer Roselia to Roserade.
I do like Sceptile as well but Grovyle is just an amazing design.
Same here, I really like Dragonite as well but Dragonair just has a majestic aura.
I love Bisharp! To me it’s a much better design than kingambit, almost reminds me of Scizor but mixed with samurai armor. Dark and steel, two of my favorite types, he always has a place in my team when playing BW/B2W2. Plus, pawniard is a cute little fella 
10/10 pokemon for me!
Dragonair is the easy answer, personally I hate Dragonite even not taking into account that it evolves from the gorgeous Dragonair. But even if I did like it, it just does not look like it belongs in the same evo tree. Surely gen 10 is the one they make the regional dragonite variant that looks like dragonair or a split line like hydrapple. (Please Gamefreak I have waited over 20 years you owe me this)
A less common answer is that Porygon 2 is one of my top 20 pokemon overall, but I do also like Porygon-Z, in fact I love the entire Porygon line. I do kind of want them to make a alternate Porygon 2 evo where it doesn’t get corrupted, but I doubt such a thing will ever happen. Who knows though, Farfetch’d got an evo and outside of me I don’t think he had too many fans before Sirfetch’d was released.
Jigglypuff and cascoon are pretty great, also technically Pikachu is a middle evolution which is a little weird to think about
Cheers!
Sorry haha, it all stems from when I was a kid playing fire red and evolved my dragonair thinking it was going to become gyarados, and instead getting a silly orange dinosaur instead lol.
I can at least say that he has a good vibe to him, even if he’s not one of my favorite designs.
You know, I didnt even think of pikachu, but to be fair he used to be a base pokemon! Sidenote I might be in the minority on this, but Raichu is my favorite of the pika line. I just love his colors and ears especially.
I really like Pidgeotto. It was a mainstay on Ash’s team for the entire Indigo League. Pidgeot is awesome too but he released it immediately after evolving so I always had more of an attachment to the former.
Definitely one of the most memorable middle evolutions for early route birbs.
I agree with a few others here who have mentioned Dragonair.
Another one though is Wartortle. It has unique features which are lost with its evolution.
Kadabra always seemed more “energetic” to me, like a magician in it’s prime. Alakazam looks like an old man just trying to make it to retirement.
Not saying it’s the peak of the line or definitely that it shouldn’t evolve but if we are talking about middle evolutions i’m glad to whip out betobebi to make grimer my favourite middle evolution! Poor betobebi never got a real chance
Haunter
Poliwhirl
Dragonair
Rhydon
Magneton
Also, looking at others’ suggestions, Gen 4 made this question pretty easy by introducing so many lesser evolutions for previous-gen Pokemon. Most are just “okay” but nothing that excited me back then nor now.
Because of the Robin Hood episode in Doctor Who I named mine Capaldi. So “old man” is fine for me. 
And of course I agree on Dragonite.
Gabite and Fraxure
Every day marshtomp reminds me to be grateful that they didn’t massacre my boy with the bipedal crap they like to do
