Odd One Out

[NoOneAtAll]

Samurott is the only one having a hidden ability that has nothing to do with water (Protean can change the user into a water type, rain dish is also typically water, shell armor just blocks crits).
Noctowl, Swellow, Fletchinder?

 

[Sapph the Knight]

Fletchinder's the only one who isn't part normal.

Mamoswine, Tangrowth, Yanmega

 

[NoOneAtAll]

Mamoswine is the only one having a higher attack than defense stat.

Mareep, Electrike, Dedenne.

 

[Sirfetch’d]

Dedenne doesnt evolve!

Pachirisu, Chatot, Bibarel?

 

[Percy]

Bibarel is the only one who has a pre-evolution form.

Swellow, Porygon, Machamp.

 

[Sirfetch’d]

Porygon is a base stage Pokemon!

Alakazam, Reuniclus, Gothitelle?

 

[Lycanthropy]

Reuniclus is the only non-humanoid of the three.

Weezing, Claydol, Bronzong

 

[Starry Windy]

Weezing is the only Poison-type Pokémon among the three.

Magikarp, Basculin, Goldeen.

 

[Nidorina of Time Lord]

Basculin is not from generation 1, like Magikarp and Goldeen are

Durant, Genesect and Forretress

 

[Aslan]

Forretress is the only one that doesn't look like it'll eat your soul!

Luvdisc, Buneary, Happiny.

 

[Percy]

Mantyke is a water Pokemon!

Deoxys, Mewtwo, Arceus.

 

[Sirfetch’d]

Arceus has the most formes!

Totodile, Tentacool, Tympole

 

[Starry Windy]

Tentacool has Poison type along with Water type, unlike the other two.

Lucario, Gardevoir, Fearow.

 

[Sirfetch’d]

Fearow doesn't have a mega evolution!

Dugtrio, Dodrio, Pidgeot

 

[Lycanthropy]

Pidgeot is the only one with only one head.

Skarmory, Probopass, Magnezone

 

[Aslan]

Probopass is the only one with nose hair. 8)

Breloom, Aerodactyl and Blaziken.

 

[Etherion]

Breloom doesn't mega evolve!

R-Wash, R-Frost, R-Mow

 

[Sirfetch’d]

R-Wash isn't weak to fire!

Buneary, Bunnelby, Rattata

 

[Pendraflare]

Bunnelby evolves into a Pokémon that has a second type.

Weezing, Gengar, Crobat.

 

[Nidorina of Time Lord]

Weezing is part of a two stage line. The others are three stage.

Venomoth, Butterfeee and Mothim