Hornets aren't bees, they're especially large wasps. Correct. Bees only attack in self-defence, and even when they do they die. All they want to do is get on with their lives and go around pollinating flowers and drinking their nectar, and will go to great lengths to get to those flowers (if you stand between a bee and a flower they'll just fly around you). They make honey that people enjoy eating, and are generally wonderful to have around. I once was stung by a wild bee out in the New Forest, and they're a bit more temperamental, but they still just want to get on with their lives. Wasps on the other hand are hideous, and I'm bleeding petrified of them. I'd probably have a heart attack if one the size of that one in @NIGHTBRINGER's meme appeared outside my house, and if I were to face a Harry Potter Boggart it would definitely turn into said giant wasp. True, they attack and eat mosquitoes, but they'll also have a go at pretty much any other bug their size. I've seen one attacking a grasshopper, and another time a caterpillar fell from a tree and bounced off my head onto the ground, and I saw that a wasp was on top of it - when the wasp flew off the caterpillar just lay there paralysed from the wasp sting. Grimdark as hell. Hornets of course are massive ones that sting even more painfully. I saw one once on the other side of my bedroom window, it scared the living daylights out of me, but luckily I've never seen once since. That's one of the reasons why I don't mind spiders - they'll happily eat wasps that get stuck in their webs and reduce their surface population, and good luck to them. Funnily enough just as I've been typing out this post a wasp was trying to get in through my window, but I managed to shut it again before the bastard could get in.
My boggart would either turn into me dying alone or a Lustria-Online where no one reads my indexes, fantasy world thread, and everyone stops reading and writing fluff pieces.