Giant bug? Check!
Actual giantest bug there even is, the largest of the order Hemiptera? Check!
Giant claws and bitey bits? Check!
Actively venomous? f**k!
Doesn't just bite or poison, but injects digestive juices that liquefy its prey from the inside through a beak that is really more of a piercing syringe? THIS WASN'T EVEN ON THE ORIGINAL CHECKLIST, BUT WE'RE DAUBING IT IN OUR MELTING BLOOD!
This picture is still better than reality because at least it's happening outside your body.
We know we have an "arachnid response" for things that are horrifying because of their fundamental alien-ness. We don't have a "giant water bug" response because everyone who's seen one is too busy looking for a heavy object and regretting not writing a will. And don't relax thinking that the giant water bugs restrict themselves to smaller prey, either. They've been seen eating things as large as snakes or even turtles, using their horror-monster face to inject flesh-dissolving horrorgoo. They've also attacked humans, and while they don't succeed in their plan to dissolve us like the Blob and slurp up the remains, the fact is that THAT IS THEIR PLAN. But instead of phase-changing us into supper, their uniquely awful poisons "only" cause hours of burning pain as bits of your body turn into flesh-smoothie.