Originally a “show-stopper” (now often spelled without the hyphen as one or two words) was a sensational musical number which created so much applause that the show had to be temporarily halted. By extension, anything making a sensationally positive impact could be called “show-stopping.”
Computer programmers flipped the meaning by labeling a bug that brings a program to a halt a “showstopper.” Now the word is commonly used as a synonym for “deal-breaker” in government and business. The negative meaning is now so pervasive that it can’t be called an error, but be aware that those who know only the show-business meaning may regard you as ignorant if you use it in this way.