The Japanese Hornet - AKA The Asian Giant Hornet:

From Wikipedia:

The Asian giant hornet (Vespa mandarinia, known colloquially as the Yak Killer hornet), the world's largest wasp, is a native of temperate and tropical Eastern Asia. Its body length is between 27 mm (1.1 inches) and 45 mm (1.8 inches), with a wingspan of about 76 mm (3 inches). Queens may reach a length of 55 mm (2.2 inches).

Sounds pretty tame, if you get past it's freakish size, but that's just the begining:

A few interesting notes on Vespa mandarinia's venom and stinger:

* The venom contains at least eight distinct chemicals, some of which damage tissue, some of which cause pain, and at least one which has an odor that attracts more hornets to the victim.
* The venom contains 5% acetylcholine, a greater concentration than is present in bee or other wasp venoms. Acetylcholine stimulates the pain nerve fibres, intensifying the pain of the sting.
* Vespa mandarinia uses its large crushing mandibles, rather than its sting, to kill prey.
* The venom of the Asian giant hornet is more toxic than that of most other bees or wasps, giving this species one of the greatest lethal capacities per colony.
* Like all hornets, V. mandarinia possesses a barbless stinger, allowing it to sting repeatedly.

Yes, at this time it is ok to scream like a girl if one or a thousand of these appear anywhere near you!

Scary enough, I've seen much bigger flying wasp things up close in person (Cicada Killer), but the thought of a painful burning sting that attracts the rest of the swarm to my fat ass - no thank you!