To get this achievement you need to play on any game made/map and have 2 females and 2 males on the same team.
The list of characters are below:
- Medic
Lazarus (male)
Caria (female)
Val (female)
- Support
Bucket (Male?)
Hank (male)
Cabot (male)
- Assult
Markov (male)
Hyde (Male)
Parnell (male)
- Trapper
Maggie (female)
Griffin (male)
Abe (male)