What episode does goku turn super saiyan for the first time?

Answer 1

Goku turns Super Saiyan on Episode 80: Transformed at Last.

Frieza miraculously survives the blow from Goku's Spirit Bomb. Frieza kills Piccolo when he pushes Goku out of the way from Frieza's attack, thus sacrificing himself in the process. He then crushes Krillin to bits which was too unbearable for Goku to handle. Krillin is one of Goku's best friends and to have to see this unleashes a transformation in Goku. He has never felt this way before causing him to transform into a legendary Super Saiyan right before Frieza's eyes. Goku realizes that Frieza has caused far too much destruction and murdered many innocent lives. He is determined to end his reign of terror for good with his new form.