This is the list of X/Y Pokemon that can only be obtained through Trading, Breeding, or other special methods. This list is mostly for me so that I can complete the Pokedex, but I know other players have been looking for a list like this, too. I'm going to start with Pokemon that must be obtained through evolution by trade, but I will update the list in the future to include the others. Here we go!'


Pokemon that must be traded to evolve.
All underlined Pokemon can only be obtained through trading. All italicized can only be obtained through breeding.

Roggenrola --> Level 25 --> Boldore --> Trade --> Gigalith
(Roggenrola can be caught in the wild only in the Reflection Cave. Boldore cannot be caught in the wild.)

Geodude --> Level 25 --> Graveler --> Trade --> Golem
(Graveler and Geodude can be caught in the wild in multiple locations.)

Machop --> Level 28 --> Machoke --> Trade --> Machamp
(Machoke can be caught in the Friend Safari, but it is easier to catch Machop.)

Gastly --> Level 25 --> Haunter --> Trade --> Gengar
(Gastly can only be obtained through Breeding. but Haunter can be caught in the wild in multiple locations.)

Abra --> Level 16 --> Kadabra --> Trade --> Alakazam
(Abra can only be caught on Route 5 or in the Friend Safari. Kadabra cannot be caught in the wild.)

Timburr --> Level 25 --> Gurdurr --> Trade --> Conkeldurr
(Timburr can only be obtained through breeding. Gurdurr can be caught in the wild in 2 locations.)

Phantump --> Trade --> Trevenant
(Both of these Pokemon can be caught in the wild: Phantump on Route 16, and Trevenant on Route 20.)

Pumpkaboo --> Trade --> Gourgeist
(Only Pumpkaboo can be caught wild. It is in Route 16 only, and can be caught in 4 different sizes.)

Special Trade Requirements Below!

Clamperl --> Trade holding DeepSeaTooth --> Huntail
Clamperl --> Trade holding DeepSeaScale --> Gorebyss
(Clamperl can only be found while fishing on Route 12.)
(Gorebyss, in Y version, can be found fishing with the Super Rod on Route 12, thought it is extremely rare.)
(Huntail, in X version, can be found fishing with the Super Rod on Route 12, thought it is extremely rare.)

Karrablast --> Must Trade for a Shelmet --> Escavalier
Shelmet --> Must Trade for a Karrablast --> Accelgor
(These Pokemon must be traded for each other to evolve; otherwise nothing happens.)

Scyther --> Trade holding Metal Coat --> Scizor
(Scyther can only be caught in the wild on Route 21.)

Horsea --> Level 32 --> Seadra --> Trade while holding Dragon Scale --> Kingdra
(Horsea can only be obtained through fishing with the Good Rod in Ambrette Town or Cyllage City.)
(Seadra can also be obtained by fishing with the Super Rod in the same towns.)

Spritzee --> Trade while holding Sachet --> Aromatisse
Swirlix --> Trade while holding Whipped Dream --> Slurpuff
(Spritzee can only be found in Y version. Swirlix can only be found in X version. Both are in Route 7 only.)

Slowpoke --> Level 37 --> SlowBro
Slowpoke --> Trade while holding King's Rock --> Slowking
(Only Slowpoke can be caught wild. It's located in Azure Bay and Route 12.)

Rhyhorn --> Level 42 --> Rhydon --> Trade while holding Protector --> Rhyperior
(Rhyhorn can only be caught wild in the Glittering Cave. Rhydon can only be caught in the Friend Safari.)

Poliwag --> Level 25 --> Poliwhirl
Poliwhirl --> Give Water Stone --> Poliwrath
Poliwhirl --> Trade while holding King's Rock --> Politoed
(Poliwag can be obtained while fishing with the Old Rod in multiple locations.)
(Poliwhirl can be ontained while fishing with the Old and Super Rods in multiple locations.)

Onix --> Trade while holding Metal Coat --> Steelix
(This one is unnecessary because you can trade for one with the super common Bunnelby in (which town?) Town early in the game with an NPC.)

Pokemon that can only be obtained through Breeding.
There are some Pokemon I have not listed that have special requirements and hold items to obtain them through breeding. I have left them out because they can be obtained by catching them in the wild, and therefor, there is no need to breed for them for the much more lengthy process of completing the Pokedex.

Surskit (Breed a Masquerain; Masquerain can only be found by surfing on the pond in Route 3.)
Pichu (Breed a Pikachu or Raichu.)
Diglett (Breed a Dugtrio.)
Magnemite (Breed a Magneton or Magnezone; it will only breed with a Ditto.)
Gastly (Breed a Haunter or Gengar.)
Timburr (Breed a Gurdurr or Conkeldurr.)

Special Breeding Requirements!
These all require the parents to hold a specific Incense while in the Day Care, otherwise the eggs they will produce will just be a repeat of themselves, and not a prior evolution. These incenses can all be obtained at an outdoor vendor's stall in Coumarine City.

Wynaut (Breed a Wobbuffet; the parents must be holding Lax Incense.)
Mime Jr. (Breed a Mr. Mime; the parents must be holding Odd Incense.)
Bonsly (Breed a Sudowoodo; the parents must be holding Rock Incense.)
Munchlax (Breed a Snorlax; the parents must be holding Full Incense.)


Pokemon that are version exclusive coming soon!
Pokemon that can only be obtained through evolving certain stones coming soon!

__________________________________________________________

And that's the complete list of Pokemon you can only evolve and obtain through trading, and ones only obtainable through breeding! Remember, this list is ONLY for the completion of the Kalos Pokedex, and not the National Pokedex. Ironically, there are only about 5 other pokemon in the National Pokedex that must be traded to evolve.