From the Super Mario Wiki
“You. Finally, I get a piece of you. Finally, we'll see who's truly stronger.”
The Koopinator, also known as the Razor Blade Brigadier, is a character from Paper Mario: The Thousand-Year Door. He is a Dark Koopatrol who joined the fighting roster of the Glitz Pit under the aforementioned alias. He is the highest ranked member of the arena's major-league and only surpassed by the champion Rawk Hawk himself. His name is likely a reference to the Terminator from the multimedia franchise of the same name.
Mario encounters the Koopinator when he travels to Glitzville in search of the Gold Star in Chapter Three. When entering the arena of the Glitz Pit for the first time, Mario and his partners witness an official match between the Koopinator and Rawk Hawk. Rawk Hawk however manages to defeat the Dark Koopatrol without much effort, thereby defending his rank. The fight plays a key role in inspiring Mario to become a contract fighter, because the Gold Star is introduced in that scene.
The player re-encounters the Koopinator after defeating the Armored Harriers and joining the major-league. He can be found in the major-league locker room and will sometimes give advice or other, less-useful remarks. After the player manages to rise Mario's rank to #2, the Koopinator can be fought in an official fight. If Mario defeats him while obeying Grubba's instructions, he will become the top-fighter of the major-league and get the chance to fight Rawk Hawk.
The Koopinator can also be re-fought after Chapter Three, if the player decides to join the Glitz Pit fighters again and reclaim the title of the champion. Other Dark Koopatrols appear in the Pit of 100 Trials, but they are not related to the Koopinator.
Like a regular Koopatrol, the Koopinator looks like a Koopa Troopa equipped with heavy gear. Most parts of his body are covered by metal, with only his arms, tail, and lower jaw showing a regular Koopa's orange tone. To round off his full-body protection, he wears a darkpurple shell featuring pointy spikes. The Koopinator has also signal red glowing eyes, which are his "most charming features", as written in the Tattle Log.
The Koopinator seems to follow a stern warrior code, implied by many remarks he makes throughout chapter three. He also adheres to a strict training regime, probably based on the code of ancient Japanese samurai warriors. He often speaks calmly and with a degree of honour, and he also seems to meditate before important battles, as shown before his fight against Mario. After Mario defeats him, he reacts angrily and vows to avenge his defeat and reclaim his rank.
Names in other languages
The Razor Blade Brigadier