Spaceman with gun - betrayed by alien

[BigHouse9]

Cannot seem to find this story anywhere. A spaceman crash lands (I think) on a planet and cannot survive in the atmosphere so he wears his spacesuit all the time. He befriends an alien named Cessyn (something like that name). Cessyn has the spaceman kill all his enemies and the take the stripes or chevrons off of the aliens as trophies. Cessyn betrays the spaceman and takes the gun but the spaceman survives and makes it his goal to hunt down Cessyn.

Anyone?

[BigHouse9]

Finally found it - "Thus Love Betrays Us" by Phyllis MacLennan