Odd one out!

Sliggoo evolves from Goomy at level 40, other two evolve from 30

Ampharos, Tyranitar, Sceptile

I'm guessing Tyranitar because his Mega isn't part Dragon.

Qwilfish, Tentacruel, Mareanie

Qwilfish is the only Pokemon that isn't part of an evolutionary line.

Skarmory, Swellow, Pelipper

Skarmory was not introduced in Generation III. It also does not have a pre-evolution.

Steenee, Gothorita, Kirlia

Steenee is a Grass type while the others are Psychic type.

Raichu, Raikou, Darkrai

Raichu is the only one with an Alolan form

Audino, Miltank, Kangaskhan

There are quite a few things I can think of, but what's most apparent to me is the gender differences. Audino is odd because it can be either male or female. Miltank and Kangaskhan are exclusively female.

Gengar, Mismagius, Spiritomb?

Spiritomb is not part of any evolution line. It also cannot casually be found in the wild unless you complete some specific steps to find one.

Probopass, Stakataka, Bastiodon

Stakataka doesn't have the ability Sturdy nor was it introduced in Generation IV.

Gyarados, Pelipper, Mantine

Mantine was not introduced at the same time as it's pre-evolution, Mantyke. The pre-evolution of Mantine cannot breed, whereas Gyarados and Pelipper's pre-evolutions can.

Ninetales, Sandslash, Dugtrio

Sandslash's name doesn't contain a number. Or Ninetails isn't a Ground type.

Abomasnow, Vanilluxe, Mamoswine

Vanilluxe is pure ice right? The others are dual types.

Hawlucha, Lucario, Gallade

Hawlucha has no pre-evolution and Mega Evolution.

Electivire, Ampharos, Xurkitree

Xurkitree is an Ultra Beast and has no pre-evolutions.

Delibird, Jynx, Piloswine

Jynx isn't a Pokemon from the second generation.


Golduck, Floatzel or Clawitzer?

Clawitzer is not part of the Field Egg Group.

Aurorus, Lapras, Abomasnow

Lapras does not have a pre-evolution. (It should though!)

Eevee, Farfetch'd, Girafarig

Farfetch'd's name isn't a palindrome.
Groudon, Xerneas, Necrozma

I'm sure the last one is a mascot of a third version/sequel.(or I guess both for this case) while the other 2 are exclusives to the first set of games in a generation.

Meganium, Vileplume, Abomasnow

Meganium doesn't have a dual typing!

Mawile, Zangoose, Spinda