Odd one out!

[Absolitetion]

Araquanid is the only one walking on six instead of four.

Luvdisc, Corsola, Alomomola

 

[PageEmp]

Corsola isnt pure water

Snover, Snorunt, Sneasel

 

[miragespot]

Snorunt (doesn't have a secondary type)

Empoleon, Emolga, Emboar

 

[FeraligatrMaster]

Emolga is not a starter.

Togekiss, Yanmega, and Gliscor

 

[KNS27]

Only Togekiss that have 3-line Evo

Gallade, Lucario, Machamp

 

[miragespot]

Machamp isn't a Gen 4 Pokemon.

Graveler, Marowak, Pichu

 

[PageEmp]

Pichu is not a Ground type!

Bronzong, Cinccino, Pangoro

 

[CF1994]

Bronzong has no gender.

Heracross, Buzzwole, Pheromosa,

 

[miragespot]

Heracross is not an Ultra Beast.

Shinx, Pachirisu, Minun

 

[Damien.aspiring.fandev]

Shinx isn't available as partner pokémon in the Ranger games.
(even if befriended pokémon can be asked favors endlessly pretty much like partners...)
Also, shinx doesn't have the electric cheek pouches.

Clauncher?Pffft, this isn't "hug or kill".

Okay, hint : this one involves transportation in a long-forgotten sidegame
(however there's an other more obvious difference you might have already noticed)
Staraptor, dodrio & floatzel

EDIT: Guys, please help keeping this topic alive! Thank you very much indeed!
EDIT serie2: Need hints? Remember : the possible answers can be multiple...
for instance, shinx doesn't have the electric cheek pouches pachirisu and minun have,
but minun is the only one from a different generation.

 

[miragespot]

Staraptor has two pre-evolutions, not just one.

Azurill, Togepi, Happiny

 

[Damien.aspiring.fandev]

Post gen6, happiny is the only non-fairy type of the three.
Pre gen6, azurill is the only one lacking the normal typing.

I need ideas, I need ideas...
Eevee, totodile, torchic.

 

[PageEmp]

The first one is not a starter in the main series games

Gabite, Drapion, Starmie

 

[Damien.aspiring.fandev]

Gabite is from a three-stages evolution tree.

Weezing, arbok, math.

 

[FeraligatrMaster]

Math is not a Pokemon.

Blastoise, Golem, and Octillery

 

[CF1994]

Golem is not a Water Type.

Barbaracle, Omastar, Carracosta

 

[Zoroark Cutie]

Barbaracle is the only one that is not a fossil Pokemon

Primape, Lumineon, and Musharna

 

[CF1994]

Musharna evolves from Munna when a Moon Stone is used, as opposed to levelling up.

Steelix, Scizor, Probopass

 

[Esper]

Probopass doesn't require a Metal Coat to evolve.

Zubat, Jigglypuff, Staryu

 

[CF1994]

Jigglypuff is not owned by Ash or any of his closest companions.

Ariados, Shedinja, Golisopod