Kurtis

 Kurtis first appears as a boss character in Disgaea: Hour of Darkness. He comes from a futuristic Earth which has recently had many problems, which some think the best solution to is to find another home for humans. He used to admire Gordon, the 37th defender of Earth, but after a terrorist attack left his wife and daughter dead, and a large portion of his body destroyed, his admiration turned to hate. He is much more serious than Gordon, and also much smarter, being a scientist before being selected as the 38th defender of Earth.
 
He blamed Gordon for not being able to stop the attack, and decided he would try to surpass him as a defender of Earth. His decided to aid in the invasion of the Netherworld, which would serve as a new home for humans. Shortly after the invasion begins, he confronts Gordon, who was currently defeated by and working as a vassal of Overlord Laharl. Before fighting him, he wanted to test Gordon's abilities by sending EDF Soldiers after him. After Gordon and the others were able to fight through the soldiers, he finally decides to fight them directly (though not alone, as is the case with most boss fights in the Disgaea series). He loses the battle, but kidnaps Jennifer, Gordon's assistant.
 
Gordon and the others followed him back the the EDF's flagship, Gargantua, where he was once again beaten, and convinced that invading the Netherworld is the wrong way to save humanity. The battle took its toll on him, and instead of joining them in trying to stop the invasion he had to stay back and rest for a while. The reason Kurtis kidnapped Jennifer was so she could be "modified" with a mind control implant. Being very skilled in martial arts, she was more than a match for Gordon, but Kurtis arrives and uses his last bit of energy to disable her implant.  He dies afterwords, and Gordon decides to make him the 38th defender of Earth in honor of his sacrifice.
 
Later in the game, when the group is faced by several greater demons and considers running away, Kurtis returns as a prinny and gives them a short pep-talk before joining them.
 
In Disgaea 2: Cursed Memories the player is able to use one of the cellphone items to call him for help. If you call him enough times, you can unlock extra stages where you need to save him from copies made by the EDF. on the final extra stage, Gordon, Thursay, and Jennifer also join the fight.