Odd one out!

[Ace Trainer 188]

Yveltal isn't part Psychic.

Alolan Dugtrio, Diggersby, Sandslash

 

[CF1994]

Diggersby is not part of the original 151 Pok?mon.

Malamar, Hoopa, Lunala

 

[FeraligatrMaster]

Malamar is not a legendary.

Pichu, Grubbin, and Magnemite

 

[CF1994]

Pichu's evolution does not require an electric/magnetic location to evolve.

Pupitar, Shelgon, Charjabug

 

[IlluminateRipple]

Charjabug isn't part of a pseudo-legendary line.

Medicham, Flygon, Pinsir

 

[Arma]

Pinsir is the only single typed Pokemon of the three!

Rapidash, Zebstrika or Mudsdale?

 

[CF1994]

Mudsdale does not have an Ability that grants immunity to its own elemental typing.

Slowpoke, Mudkip, Corphish

 

[Ace Trainer 188]

Mudkip is the only one that evolves twice.

Machoke, Arbok, Dragonair

 

[Damien.aspiring.fandev]

Machoke has arms & dem legs (and is the only one with pawprints of the three)

Serperior, chimeco, chatot.
(one of them leaves a mark behind, and two share the same faction)

 

[Arma]

Serperior is the only one that doesn't have the letter c in its name! =D

Doduo, Zweilous, Fearow

 

[Damien.aspiring.fandev]

Zweilous is dragon/dark rather than normal/fug flying,
and they hail from a different generation than the other two.

Ninjask, scyther, paras.

They're found in a miniscule 4-settlements region that appeared in a long forgotten
sidegame. One of them has a different pokéassist, and an other lacks a field move.
Said region doesn't have a league.

 

[Arma]

Ninjask, scyther, paras.

They're found in a miniscule 4-settlements region that appeared in a long forgotten
sidegame. One of them has a different pokéassist, and an other lacks a field move.
Said region doesn't have a league.

Interesting lil' tidbits of vague information! Too bad I can't make head nor tail of it. n_n"
I'll go with Paras here though, the other two both change types upon evolution. That and they got wings.

Wailord, Celesteela, Golem

 

[KorpiklaaniVodka v2.0]

Celesteela's an ultra beast the other two aren't.

Latias, Heatran, Keldeo

 

[CF1994]

Heatran is not outright associated with any other group of Legendary Pokémon, whereas Latias is related to Latios, and Keldeo is part of the Swords of Justice quartet.

Araquanid, Ribombee, Vikavolt

 

[Damien.aspiring.fandev]

Araquanid isn't airborne.

Cubone, pikachu, skitty.
*bulbagarden.net image removed*~°~*bulbagarden.net image removed*~°~*bulbagarden.net image removed*

One of the three was available as playable character solely in two sidegames
from the same series, these being counterparts to each other.

 

[CF1994]

Skitty was not introduced in Generation I.

Ferrothorn, Toxapex, Turtonator

 

[KorpiklaaniVodka v2.0]

Ferrothorn's name doesn't start with T lol

Sharpedo, Crawdaunt, Ludicolo.

 

[CF1994]

Ludicolo is not a Water/Dark-type.

Ninjask, Scolipede, Vikavolt

 

[faf]

Vikavolt doesn't get access to Speed Boost.
Hydreigon, Kommo-o, Haxorus

 

[CF1994]

Haxorus is not a Pseudo-Legendary and also lacks a dual typing.

Absol, Houndoom, Liepard