What a ghastly name you may think for such a pretty, irridiescent insect. But the TH is not named for it's resemblance to the (unnecessarily big and heavy) arachnid. Small mercies.
The females are such hard bastards that they prey on tarantulas. With a hawk-like tenacity. RUN. RUN AWAY SPIDER FRIENDS. When they reach wasp puberty, they get their mate to tattoo their nickname onto their wasp forehead using a bic biro and a sharpened fork tine. Then it's egg-laying time they go hunting for our 8-legged friends. They even pretend they are hurt near a taranula's house, to lure Mr or Mrs Spidey out. When they find their horror-show target they STING IT 'between the legs' with a 7mm long stinger. Now paralysed, Spidey is dragged into the well-prepared serial-killer's burrow. Licking it's fiendish no-lips, the ferocious Jasper lays one tiny egg on the spider's tummy. Then, laughing until snot comes out of it's wasp nose, it seals up the burrow.
Some time later, the larva hatches out, EATS A TINY HOLE into the spider and starts feeding off it's delicious spider goo. Our tarantula friend is alive (probably sincerely wishing otherwise) the whole time, and the larva leaves the organs until last.
Finally dead, the spider isn't aware of the chunky, grown up wasp eating its way out of it. After it's nightmarish start in life, the wasp then bumbles around merrily drinking nectar all day. Despite, this it has really bad halitosis. How does it go from finding innards scrumptious to only fancying flower sugar?
Ah, but it's just tarantulas it bothers right? Not if you menace it, and even accidentally, like if you spill its pint. Not only will it then sting you, and probably in the face, it has the SECOND MOST PAINFUL STING in the world. There's a dreadful list you'll wish wasn't a thing called the Schmidt Sting Pain Index. You're welcome.
I give the Tarantula Hawk a clean 6/10 for nastiness. The modest score is mostly due to it not being known in the UK.