Odd One Out

[Admison]

Taillow is the only one who doesn't have three evolutions.

Sandslash, Persian, Marowak

 

[Meadow]

Metang isn't a part of Bronzor's evolution line.

Caterpie, Paras, Sewaddle

 

[bunny24680]

Caterpie as it's not grass type.........

Try this: Ralts, Kirlia, Gardevoir.

 

[Meadow]

Gardevoir is the only one who can't evolve into another species. /carefully worded

Gallade, Hitmonlee, Medicham

 

[DyingWillFlareon]

Medicham doesnmt have a split evolution line.

Aipom, Cyndaquil, Teddiursa

 

[TheFunnyFeraligator]

Cyndaquil, because he is not a normal-type.

This one's not about the types OR evolutions
Clawitzer
Starmie
Dragalge

 

[DyingWillFlareon]

Starmie is not version exclusive to anything.

Sneasel, Totodile, Mareep

 

[Meadow]

Mareep is the only one that doesn't learn any Dark-type moves via leveling up.

Roserade, Walrein, Aggron

 

[DyingWillFlareon]

Weezing is the only one weak to Dark type moves.

Paras, Chikorita, Sandshrew

 

[Meadow]

Chikorita is the only Pokémon that was introduced in Generation II.

Sharpedo, Garchomp, Kingdra

 

[DyingWillFlareon]

Sharpedo is only a two evolution stage Pokemon line.

Skitty, Mudkip, Carvahna

 

[TheFunnyFeraligator]

Skitty isn't a water type.

Girafarig
Poliwrath
Skarmory

 

[DyingWillFlareon]

Poliwrath, as it is the only on to share the first letter of it's name with a Pokemon game that has not yet been remade.

Aron, Torchic, Shroomish

 

[bunny24680]

Torchic, as it is a starter pokemon in a main game while othets are not.

Try this: caterpie, weedle, nincada

 

[DyingWillFlareon]

Caterpie doesn't have a second type.

Duskull, Treecko, Poochyena

 

[Lycanthropy]

Poochyena doesn't have a third evolution.

Breloom, Skarmory, Vileplume

 

[Meadow]

Skarmory doesn't have an evolution line to begin with.

Groudon, Dialga, Zekrom

 

[Brojman]

Golbat

 

[TheFunnyFeraligator]

Groudon, he is the only legendary of those three who doesn't have the dragon type.

Poliwrath, as it is the only on to share the first letter of it's name with a Pokemon game that has not yet been remade.

Actually, it was Skarmory, because he is the only one that still continues to have a unique type combination. Good guess, though!

Here are my next ones. This one's about evolution!
Clefairy
Jigglypuff
Marill

 

[DyingWillFlareon]

Marill is the only one who evolves without a stone?

Munchlax, Turtwig, Bonsly