What Pokémon Have had the Greatest Drops in Tiers in-between Generations?

Question

What I mean by this is that most Pokémon usually stay in or around the same time for each Generation. I want to know which Pokémon have had the biggest drop in tiers between Generations. Please list the top 5, which tiers the dropped to and from and why. For example, this question showed why Politoed dropped severely.
https://pokemondb.net/pokebase/368707/why-did-politoed-drop-to-untiered-in-generation-6

Comments

Rotom-Frost fell from OU (DPPt) to Untiered in BW because of it getting the Ice-typing, which made it Stealth Rock weak and horrific defensively.

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I don't think forms should count because they have different typings, moves, roles, etc., So forms don't count.

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Can someone tell me why is X's answer a comment?

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My "answer" is a comment because I'm not sure whether or not those are the highest. I haven't looked through every single Pokemon's tier changes between generations, so I cannot answer with certainty. I am, however, confident that Wobbuffet, Dugtrio, and Politoed are three of the largest five drops. The question also asks for the reason why those Pokemon dropped so far, and while I may be able to answer that if I knew all five, I cannot at the present moment, and as such my comment is just a comment.

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Hi I just started the research and I'll complete it in 15 mins or more.

Answer 1

I'm going to answer this, as the existing answer is somewhat incorrect, both in Pokemon and in reasoning.

Wobbuffet was UUBL in BW, then Untiered in XY.
Politoed was OU in BW, then Untiered in XY.
Leafeon was UU in DP, then Untiered in BW.
Dugtrio was OU in XY, then Untiered in SM.
Gothitelle was UUBL in BW, then Untiered in XY.
Charizard was UUBL in RS, then NU in DP.

Wobbuffet: In BW, it was UUBL because of the Encore nerf. It faced competition from Gothitelle, a more offensive Shadow Tag user. Despite this, it managed to hold its own in OU. However, in XY, Shadow Tag was banned in all tiers except Ubers. While it was somewhat viable in Ubers, it was heavily crippled in all other tiers, thus shooting it and Gothitelle down to Untiered. Shadow Tag was later banned in Gen 5 OU as well, but that happened after the Gen VI metagame began.

Politoed: Weather teams became less common in XY with the weather nerf, meaning Politoed was used on fewer teams. Drizzle was also banned in all tiers except OU, and so Politoed struggled to find a niche anywhere, and as such went to Untiered.

Leafeon: In BW, Sawsbuck was introduced. With two immunities with Sap Sipper, the same Speed and a slightly lower Attack stat than Leafeon, and Horn Leech, Double-Edge, Jump Kick, Substitute, and more, Leafeon was almost completely outclassed. It was still viable in lower tiers, but Sawsbuck could do almost everything Leafeon could, but better.

Dugtrio: Dugtrio should not have been OU in XY after the ban of Arena Trap, but it was. This was immediately remedied in SM, where it went straight to Untiered.

Gothitelle: In BW, it was UUBL because of Shadow Tag, allowing it to easily trap and KO specific opponents. In XY, Shadow Tag was banned in most tiers, and without it, Gothitelle couldn't find a niche, and fell to Untiered. Shadow Tag was later banned in Gen 5 OU as well, but that happened after the Gen VI metagame began.

Charizard: Two words: Stealth Rock. Charizard took 50% damage every time it switched into a field with Stealth Rock up, making it very easy to KO. It could still be useful with Rapid Spin support, but Stealth Rock greatly crippled it. It was better in RS because there was no Stealth Rock.

I'll keep researching, and if I find any drops more drastic than the ones on this list, I'll edit it.

Hope I helped!

Comments

Thanks!

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You're welcome!

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I can help you with some examples:

Shuckle was RUBL in the 6th Generation after having gained Sticky Web, but was Untiered in Gen 7
Talonflame went from RUBL to PU from Gen 7 to Gen 8
Sylveon dropped from UU to NU from Gen 7 to gen 8
Celebi dropped from UU to NU in gen 8, after being a staple of Gen 7 UU
Porygon-Z dropped to NU in Gen 8 after being UUBL in Gen 7

Some honorable mentions include Aegislash (before it got banned from UU) and Blaziken (currently being suspect tested)

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Just so you know, shadow tag was banned in gen 5 OU, but it was after gen 6 started.

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Edited!

Answer 2

Wobbuffet was UUBL in BW, then went to Untiered in XY.
Leafeon was UU in DPP, then Untiered in BW.
Dugtrio was OU in XY, then Untiered in SM.
Politoed was OU in BW ,then Untiered in XY

gothitelle was UUBL in BW, then untiered in XY
Mr.mime was NU in DPP, then untiered in BW
Reasons
For wobbuffet its ability was banned from lower tiers so without shadow tag, it was bad and just basically almost all status move fodder like hazards and set-up
"Dugtrio: Dugtrio should not have been OU in XY after the ban of Arena Trap, but it was. This was immediately remedied in SM, where it wen straight to Untiered."

For Mr.mime it just managed to get by. Poor defence and hp stat. As well as decent s.atk didn't do much for it.
It also got out classed by other better psychic types like musharna and even kadabra.
Gothitelle was not much without its ability shadow tag similar to dugtrio. It didn't have much offensive powers so it fell to untiered.
"Leafeon: In BW, Sawsbuck was introduced, and with two immunities with Sap Sipper, the same base Speed as Leafeon, and only a slightly lower Attack than Leafeon, Leafeon was essentially completely outclassed. Sawsbuck got Swords Dance, Double Edge, Horn Leech, Substitute, etc. -- most moves that Leafeon could learn, and as such there was almost no point in using Leafeon over Sawsbuck."
"Politoed: Politoed was Untiered in XY . Rain teams were becoming more uncommon in the XY era because of the weather nerf. Drizzle was also banned in all tiers below OU, so Politoed struggled to find a niche anywhere."
Source: smogon pages and X's comment
note : all "" are from X's comment
Hope I helped!

Comments

How did Rampardos fall harder than Gothitelle or Leafeon? Both went from UU (Gothitelle from UUBL) to Untiered.

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Oh ho missed em I guess 1 sec. Thanks for telling

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I don't really think that the reasons given in these answers are quite right, so I'll try to add on to them.

Leafeon: In BW, Sawsbuck was introduced, and with two immunities with Sap Sipper, the same base Speed as Leafeon, and only a slightly lower Attack than Leafeon, Leafeon was essentially completely outclassed. Sawsbuck got Swords Dance, Double Edge, Horn Leech, Substitute, etc. -- most moves that Leafeon could learn, and as such there was almost no point in using Leafeon over Sawsbuck.

Dugtrio: Dugtrio should not have been OU in XY after the ban of Arena Trap, but it was. This was immediately remedied in SM, where it wen straight to Untiered.

Politoed: Politoed was actually Untiered in XY, not PU. Rain teams were becoming more uncommon in the XY era because of the weather nerf. Drizzle was also banned in all tiers below OU, so Politoed struggled to find a niche anywhere.

Rampardos: Rampardos wasn't ever UU. In DP, it was NU, which means going to Untiered wasn't a huge drop.

Gothitelle: In BW, it was UUBL because of Shadow Tag, allowing it to easily trap and KO specific opponents. In XY, Shadow Tag was banned in most tiers, and without it, Gothitelle couldn't find a niche, and fell to Untiered.

Mr. Mime: It was NU in DP, not UU. It was UU in RS.

I'm not exactly sure why Wobbuffet and Mr. Mime fell so far, but I hope I've clarified a bit on the others.

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I'll select this if they edit these reasons in instead of their own (Which are definitely aren't right as you said) and come up with why Wobbuffet and Mr. Mime dropped as well as get replace Rampardos, which is wrong.

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sure done

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If you're going to use my comment as a source, put my words into a blockquote :P

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done that too :P