In the 1980s, the Soviet Union had a few problems. For starters, their anti-ship missiles couldn't quite cut it. Now, it's not that the Russians built bad missiles — the SS-N-2 Styx had sunk an Israeli destroyer in 1967, shortly after the Six-Day War. The problem was that American (and NATO) surface-to-air missiles had more than caught up, meaning the Soviets were effectively outranged.
In addition, the arrival of the French Exocet, West German Komoran, and the American Harpoon changed the game. These missiles didn't quite have the range or warhead of the AS-4 or AS-6, designed specifically to kill American carriers, but there were a lot of them. Worse, they were being back-fitted on just about every NATO ship or plane, giving them a lot more assets. Plus, they flew very low, skimming over the surface of the ocean.
The Soviets realized they were getting left behind in the anti-ship missile department, and that put them at a huge disadvantage.
So, Russia began work on their own version of the Harpoon in the 1980s. However, after the Soviet Union fell, the missile's introduction was delayed until 1997. Russia eventually got its "Harpoonski" and soon, older Krivak-class frigates and newly-build Gepard- and Neustrashimyy-class frigates were being equipped with this missile, known as the SS-N-25 Switchblade.
Quickly, many countries found that a quad-pack of SS-N-25s could replace a single SS-N-2 launcher. Algeria made such a swap on their Nanuchka-class corvettes. Russia also began to export corvettes, like the Tarantul-class, that could carry 16 of these missiles.
The Russians also came up with an air-launched version, the AS-20 Kayak. This gave Su-33 Flankers operating from the Kuznetsov a capable anti-ship weapon. Su-24 Fencers and MiG-29 Fulcrums transferred to Russian Naval Aviation also got this weapon. It also saw export sales to India, Vietnam, and other countries.
The Switchblade also became a coastal-defense system. The SSC-6 Sennight can be mounted on trucks and used to attack ships 75 miles away. Russia has also developed an extended-range version that can go up to 180 miles.
In short, Russia's Harpoon is one lethal missile.