This doesn't need to be done in a single match, it can be done over a number of matches.
You need to use your ultimate/4 to get a kill on a enemy God.
If you haven't played this God since his release they changed how this ability works, it used to home in on other Gods but not it's a small aimmable AOE. You last a good while flying in the air after you use it and it doesn't do all too much damage. A lot of luck goes into getting even just a single kill with this ability so you may have to play many matches to get the ten required.
To check progress outside of a match go to your profile and then the "Achievements" section, next go to "Kills Progress" witch is the one with the two swords behind a spartan style helmet.