The IF Prototype LQ-84i K-9000, also known as Bladewolf, is the first boss character that Raiden fights in Abkhazia and the end of the demo in Metal Gear Rising Revengeance. He also happens to be a playable character in optional DLC.
Having been designed for combat, Bladewolf was unique in that he was allowed to think and act autonomously to a small extent. The "Winds of Destruction" treated him as something of a pet, as Mistral and Sundowner often kept him around for training. At one point, Senator Armstrong even placed him in the sewers when "Jetstream" Samuel Rodrigues arrived to infiltrate World Marshal HQ in Denver, Colorado, but Bladewolf was quickly defeated by the Brazilian samurai.
Sometime later, Bladewolf was run through a series of VR training exercises overseen by Mistral. She then took him to Abkhazia with her, as cyborgs from their employers at Desperado Enforcement LLC were tasked with overrunning the country supposedly at the request of a rebel leader. Bladewolf's earlier talks with Mistral and another soldier nicknamed "Khamsin" about bringing freedom to the country caused him to start questioning his own obedience, and then he decided to take advantage of a distraction to crush Mistral's control remote and run away.
Mistral's forces pursued Bladewolf to the coast of Abkhazia, but Bladewolf cut through them and kept running until he found himself face-to-face with Khamsin himself, a cyborg soldier attached to a gigantic suit of powered armor. Bladewolf managed to kill Khamsin, but then Mistral used a backup device to reassert control over Bladewolf, having staged his brief escape as an excuse to eliminate Khamsin for unknown reasons.
Some time later, Bladewolf was ordered to kill Raiden when he entered the territory, but Raiden cut him into pieces, keeping his AI alive. As thanks, the Doktor placed Bladewolf's AI in a reassembled dog-like robot body. After that battle, Bladewolf decided to assist Raiden in his mission, scouting ahead and offering advice when requested.
Eventually, Bladewolf reappeared at the Pakistani army base, having been damaged by Senator Armstrong himself. He manages to stay up just long enough to play a pre-recorded message from then-dead Jetstream Sam and toss the HF Murasama Blade to Raiden before Armstrong permanently destroys his body.
After Raiden finally defeats Armstrong, enough of Bladewolf is salvaged to reconstruct his body again, and he is seen talking to Sunny Gurlukovich in her office at Solis.
Bladewolf's main weapons include his teeth and claws, but also a small chainsaw that attaches to his tail, which allows him to whip the blade around and cut through enemy cyborgs. Bladewolf can also throw incredibly hot knives as projectiles, which can easily pierce through the armor of cyborg enemies. Like Raiden, Bladewolf is capable of stealth killing unaware enemies.