Go in the Raiden thread for questions about Raiden please...

I'd actually like you to do that....Use the search engine for example.

But to answer your question, it is inferred, and not confirmed that Raiden was tainted when he fought with Quan Chi and Shang Tsung in the ether. Their essences mixed or something is the speculation, but he is in fact tainted.

Thus far all we know for certain is that he's losing his patience with Earth's mortals and is taking a more ruthless "any means necessary" approach towards defending the realm. According to Fujin's Armageddon bio, it appears something went wrong while Raiden was reforming on Earth and that may be why he's changed.

Personally, my theory is while reforming Raiden was tainted by the One Being...and this more ruthless stance is just the start.