Odd One Out (minus the double posts!)

[Corrin]

Love your sig! haha

Nincada doesn't have flying as a type

Ninjask, Shedinja, Beedrill

 

[HollyYoshi]

Beedrill. It's not an evolution of Nincada.

Meganium, Tyrantum, Sammurott

 

[KetsuekiR]

Tyrantrum since it's not the final stage of a starter Pokemon.

Tyrannitar, Salamence and Metagross.

 

[Corrin]

Metagross isn't a pseudolegendary iirc

Skarmory, Spinda, Sandshrew?

 

[Arcean Warrior]

Shanshrew, because you're supposed to be Sandshrew, so basically you're the only one with a Nickname XD

Flareon, Vaporeon, Jolteon

 

[Corrin]

Vaporeon is the one one that swims? lol

Bidoof, Zigzagoon, Rattata

 

[Arcean Warrior]

Zigzagoon. Rattata and Bidoof are Gnawer Pals. No contest.

Wurmple, Scatterbug, Weedle

 

[Corrin]

Weedle is dual typed

Garchomp, Ariados, Alakazam

 

[KetsuekiR]

Garchomp is the only pseudolegendary.

Spearow, Taillow, Hoothoot

PS: Metagross is a pseudolegendary :P

 

[Zoroark Cutie]

Spearow is the only one that is fully evolved.

Zubat, Woobat, and Noibat.

 

[Corrin]

Woobat is the only one with a signature move, heart stamp!

Probopass, Bronzong, Bastiodon

 

[KetsuekiR]

Bastiodon is the only non-steel type.

Moltress, Articuno, Zapdos :o

PS: Spearow isn't fully evolved.

 

[Otamajakushi]

Zapdos isnt weak to electric attacks. (EDIT: Here's a better one: Articuno has a base sp atk of 95 while the others are 125)

Charmander, Cyndaquil, Chimchar?

 

[KetsuekiR]

Charmander is the only one with a final stage with a Mega-Evolution (that was a long shot :P)

Jolteon, Umbreon, Vaporeon?

 

[Otamajakushi]

Umbreon debuted in Gen 2, while Jolteon and Vaporeon debuted in Gen 1.

Sableye, Spiritomb, Chandelure

 

[KetsuekiR]

Chandelure was the only was with weaknesses prior to Gen VI.

Dialga, Palkia, Giratina?

 

[Zoroark Cutie]

Palkia is the only one who doesn't have an immunity.

Breloom, Verizion, and Chesnaught

 

[KetsuekiR]

Verizion is the only legendary :P

Chespin, Fennekin and Froakie?

 

[Ace Trainer 188]

Chespin is a physical attacker.

Pikachu, Eevee, Piplup.

 

[Otamajakushi]

Piplup doesn't have the ability to evolve into an electric type Pokemon.

Porygon, Porygon 2, Porygon Z