Konstantin Vladimirovich Soldatov (Doctor Kleiner)
Half-Life Wikia: Dr. Isaac Kleiner
Dr. Isaac Kleiner is one of the main characters of Half-Life 2 and its episodes. An archetypal 'absent-minded genius scientist' (although somewhat more benign), he is a prolific author of several works on teleportation and interdimensional travel, and one of the few survivors of the incident that took place in the Black Mesa Research Facility. Later on, he becomes a key (if somewhat self-conscious) leader of theResistance against the Combine, and a prime member of the Resistance science team.