Raikou Animedex
ライコウ アニメ図鑑

Note: Due to a personal preference and fondness for the original English voice cast, I refuse to acknowledge the Pokémon dub after season 8/movie 8. I won't list the dub titles for anything after that.

Voice Actor: Katsuyuki Konishi / 小西克幸

The Legend of Thunder!
ライコウ 雷の伝説
Raikou: Legend of Thunder

A group of Team Rocket are bent on capturing the elusive Raikou, through any means necessary. However, a group of three Johto trainers and Eusine come to its rescue.

Mesase Pokémon Master!, Ready Go!, ~ Pokémon Symphonic Medley ~

#180: Houndoom's Special Delivery
Hellga and Togepi!

Houndoom and Togepi briefly see a Raikou, before it promptly flees.

#227: For Ho-oh The Bells Toll
スイクンとミナキ! ホウオウの伝説!!
Suikun and Minaki! The Legend of Houou!!

Eusine and Morty tell of the legend of the Three Beasts and Ho-oh.

AG#040: Watt's With Wattson?
キンセツジム! テッセンの電撃バトル!!
Kinsetsu Gym! Tessen's Electric Shock Battle!!

Mauville Gym Leader Wattson owns several Raikoubots.

DP#137: Marill · Piplup · Elekid!!
Maril · Pochama · Elekid!!

Piplup protects Dawn from a Raikou in a nightmare.