My strategy with Raiden consists on staying as far as I can from him. If you stay close it's a death sentence, he has too much invincibility. Try to jump backwards over his green arrows. If he attempts to throw his hammer, this is your golden chance, teleport behind him and hurt him with a nice combo (I won't list any lenghty combos for you, the 3-4 hits combos available in the moves list will do just fine). If he taunts, do the same, or launch an electric bolt, or use the torpedo move. If you feel you'll get trapped in the corner, jump upwards and use the torpedo move (don't teleport...). Shao Kahn also blocks rarely when he's close to you, use an X-Ray (if available) if you're trapped in the corner and he's punching the hell out of you. The most important thing is to never trade direct hits with him.
Good luck!
PS: don't worry, his name is not a spoiler.