CAVEAT: This does NOT apply to hornets, particularly the ones that boil out of the ground. Run for the fucking hills.

I've only encountered those fuckers once in my life. They made a giant nest in a rather large sand and gravel pile on my parent's property. After a year or so of them being there, an older cousin of mine had the idea to try to take them out with slingshots. I suggested napalm.

We compromised. We whipped up a batch of improvised napalm with a bunch of kerosene and a styrofoam cooler, poured that down the main entrance of the hive extremely carefully, and lit it on fire. We then spent the next few hours taking potshots at most of the hornets that tried to flee while on fire. We made certain to kill the queen when she finally emerged, though I don't think she was long for the world anyway. She couldn't fly, and had burning "napalm" covering half of her. We still made sure to throw a large stone on her.

We did this specifically because everyone in my family is allergic to bee stings, so it was kinda an act of war for them to move into that part of our property.