He entered the Arena to escape his dull life as a company man. He lacks skill and decent equipment but his attitude has endeared him in the eyes of everyone.
Vex is a lightweight bipedal AC equipped with a small missile launcher, a hand gun, a laser blade and an overboost core.
Chris Miura is not much of a threat at all because he is poorly equipped. So you should not be scared to fight him at all because he's very easy to beat.