The name Raiden is actually that of a deity known as The Thunder God. It is rumored he received a personal invitation by Shang Tsung himself and took the form of a human to compete in the Tournament.
Teleport: Down, Up
Lightning: Down, Toward, LP
Torpedo: Back, Back, Towards
Fatality: Forward, Back, Back, Back, HP (at close range)
Fighting as Raiden
At all times be prepared to teleport behind you opponent and unleash any attack. Repeat as often as you can.
Fighting Against Raiden
When fighting Raiden, avoid his Torpedo attack as often as possible. Block the attack and counter it with a quick (but well timed) uppercut.
Raiden v.s Goro
The best tactic to use while fighting Goro is to continually use Raiden's Torpedo attack. If he gets to close, use your Lightning attack to keep Goro at a distance.
Raiden's victory comes as no surprise to him. He was never impressed by Shang Tsung's inferior sorcery, Goro's brute force, or the challenge of the other contestants. He quickly becomes bored with his mortal competition and soon invites other Gods to participate in the contest. The Ensuing battles rage on for years. And the wars result in our world's final destruction. Have a Nice Day