Well, it's a surprising choice. The computer chip has also brought education to the masses, has made other scientific and technological progress one heck of a lot easier, has arguably enriched social interaction in some ways...
These things are debatable, and of course the arrival of fast technology has seen with it the arrival of new ways for gits to exploit that technology in unpleasant ways. But the computer chip has provided far too many benefits to be called "the worst". If people behave badly, they would anyway, and one has to discount that from evaluating technology, I think.
My own choice, then, would probably be the atomic bomb. Its sole purpose is to destroy on an incredible scale, and it doesn't even get used for that, instead hanging as a threat to anyone who'd dare threaten to use their own arsenal. Not a very original choice, I'll grant you.