Normaĺly in games a player performs an ace when he kills everyone on the other team. However this is usually only in games where you only have one life, like in S+D games such as CSGO.
This game offers this achievement too but because you can respawn it is not the same becauaw you have multiple chances to kill one person.
To reserve the prestige on an ace I believe this medal should only be given to someone who kills every player on the opposing team during one spawn session. The medal then could also be given a higher reward

. But it is indeed quite easy to achieve.
