In-Game Trades - Afterbattles

Like previous games, there are a variety of points within the game where you can trade your Pokémon with various in-game trainers. However, unlike past games, once you have beaten the Elite Four, you'll be able to battle these trainers who use fully evolved forms of the Pokémon you have traded them. Not all the trainers seem to be battleable

Nacrene City - Whimsicott or Lilligant

The first trainer, アヤ, is located in the house next to the Pokémon Centre. She will battle you with Whimsicott or Lilligant in Pokémon Black & White respectively, having evolved the Cottonee or Petilil that you had previously traded her.

Lass Aya Whimsicott
Items
Level 65
Attacks:
Leech Seed
Mega Drain
Cotton Spore
Gust
Black Only
Lass Aya Lilligant
Items
Level 65
Attacks:
Leech Seed
Mega Drain
Synthesis
Teeter Dance
White Only

Driftveil City - Cinccino

The next battle is in Driftveil City. In the house southeast of the Pokémon Centre you will encounter the Youngster who you traded a Minccino with in order to obtain a Basculin from him.

Youngster Naoki Cinccino
Items
Level 65
Attacks:
Helping Hand
Tickle
Sing
Tail Slap