Burn 2 enemies simultaneously.
This trophy is missable. For this, you need an enemy encounter that provides bottles. Craft Molotov Cocktails with the bottles and throw them at 2 enemies standing close together.
You can probably grab this trophy early on during Cozumel at the second enemy encounter. There are 3 enemies and some bottles resting on a forklift. Craft a Molotov and throw it at the 2 enemies standing next to each other.