Killed many enemies in one area, and vomited.

A miscellaneous trophy earned for killing many enemy soldiers in the one area. A good place to earn this at the end of Downtown in Act 1, or Vista Mansion in Act 2. Once you kill enough, Snake will vomit automatically. Youll know you did it right if you hear Liquid Snake from the original Metal Gear Solids voice saying You enjoy all the killing, thats why. There is no specific number of kills required, as I've experienced it after as little as 40 kills, and other times experienced it after 100 kills. Do note that regardless of how many you kill, this will not occur if you are on a mounted weapon. Therefore, avoid any mounted weaponry when you are going for this. Credit to julesthegr8 for discovering this.

It is recommended you do this during your Puma/Chicken playthrough, as it will add a significant amount of kills to the required amount of 500 for the Chicken Emblem.