Fortunately for everyone, Colin was still in the thing's throat when he started to laser it to death, so the core was not cut by the laser. And fortunately for Colin, with the combined efforts of being flamethrowered in the eyes, stepped on, and lasered in the throat, it doesn't notice Meg get up there, and when it opens its mouth to attack again, it finds a sharp sword in an uncomfortable place.

Moments later, it slumps to the ground, dead from sword-in-brain.

Of course, everyone still has to deal with the immediate threat of Colin possibly suffocating in the lizard's throat, as well as retrieving the Core and doing whatever they plan to do with the babies, all before the usual wave of monsters arrive to try to claim the Core.