Xan Kriegor

Other than the fact that he was the first Champion of the Liandri Tournament, almost nothing is known about the being known as Xan Kriegor, not his species, not his background, not even his gender has been officially confirmed. He has never been seen without his one-of-a-kind cybernetic battle suit, and whispers and rumours about his true identity abound. The single most popular and most persistent rumour, however, is that Kriegor is Jerl Liandri, the CEO of the Liandri Corporation, who has secretly poured his immense wealth into the development of the most advanced combat suit in the galaxy, solely to prove his superiority in combat in the Tournament.  
 
The reality behind this combatant is far beyond what any civilian fans had guessed. "Xan Kriegor" is an entirely cybernetic being, originating as a mining robot on an asteroid designated LBX-7683. Xan's advanced design allowed him to overcome his programming and lead the other robots to a machine uprising, killing all the humans on the base. Impressed with his improvised combat skills, Liandri had him disabled, but not destroyed. Afterwards, with far more effective programming locks in place, he was quietly entered in the Liandri Tournament, where he would be able to do that which gave him the most pleasure: killing organics. 
 

He was ridiculously effective at this, and took the Championship the first year of the Tournament, successfully defending his title three years in a row after that, until being defeated in Unreal Tournament by Malcolm. The next year, an upgraded version of Xan (represented by "Xan Mark II", a free character model included in a patch) returned to try to take back the crown, but was unsuccessful. Xan sat out the following year (represented by Unreal Tournament 2003), but returned the year after that ( Unreal Tournament 2004), this time as the even more impressive Xan Mark III. He still failed to win the Championship, but this time he was at least a finalist.
 
Xan has not appeared in any Tournaments since then ( Unreal Tournament III for example), but given the insane amount of money Liandri has already poured into the merciless killing machine, it is likely only a matter of time until his return, more advanced than ever before.
 
Xan's unique voice clips generally revolve around his wild arrogance and perceived superiority to organics, most notably "You are obsolete" and "I am the Alpha and the Omega!". His appearance changes with each appearance in the series, representing the near-constant upgrades he performs on himself to become as powerful as possible. Xan is a walking representation of bleeding-edge technology, sometimes literally.