In 2267 the USS Enterprise was investigating the dissapearence fo the USS Constellation when it made a remarkable discovery - a robotic weapon of enourmous size which consumed entire planets to provide itself with fuel. The weapon used a beam of absolutely pure antiprotons to literally carve planets into pieces; a tractor beam would then gather them up and feed them to a total conversion power system within.1
The machine had attacked and largely destroyed the Constellation already. Commodore Decker, having survived the attack, took command of the USS Enterprise and launched further strikes against the machine. The battle proved decidedly unequal; the phasers of the Enterprise proved unable to penetrate the neutronium hull of the machine, whilst the antiproton weapon was more than capable of inflicting damage on the Starship.1
Whilst the Federation is capable of producing antiprotons2, as yet various technical issues remain to be resolved before antiproton weaponry can be produced.