Mode: Any, but Survival is easiest
Map: Any
Class: Pyro
Oviraptors look like this. I’d recommend killing them in Survival mode. They spawn randomly on any wave, except for Boss waves (5, 10, 15, 20, etc.). They almost always try to pounce on you, so be careful.
Alternatively you can just play Team Deathmatch as the Pyro and kill enemy player Oviraptors.
This is cumulative so the 10 kills don’t have to be in one single game/life.
You can also get the Barbeque achievement using this same method:
NOTE: If you want to get this solo,
DO NOT choose "Solo" from the Main Menu. For whatever reason, achievements can’t be unlocked in games set up through the "Solo" option.
You can, however, set up a game by yourself through the Multiplayer option. From the Main Menu go Multiplayer > Host Game > and then set up your game (make sure “Play Over LAN” is set to “No” as this seems to disable achievements as well).