In retrospect, it was not such a hot idea for a few dozen Death Eaters and their wanna bees to get snockered on fire whisky and stage a major riot at the Quiddich World Cup. Right in the middle of several thousand heavily armed fellow wizards. Hit simultaneously with hundreds of stunning spells, a number were killed instantly, but enough survived to reveal the identities of the ring-leaders.
It wasn't an auspicious start to the big V's comeback plans, but nonetheless his agent managed to penetrate the ludicrous security effort mounted by Hogwarts School's nearly senile headmaster. When the Goblet turned out to have been hexed, though, even Dumbledore's slow suspicions were awakened, and a casual seeming conversation with the Defense-against-the-dark-arts teacher revealed his rather imperfect memory of his many decades of interaction with the headmaster. Veratiserum and legilimency quickly got to the bottom of the plot and He who must not be named got a rather unpleasant surprise when he showed up at his father's graveyard. Hit simultaneously by the dozens of Aurors and members of the Order of the Phoenix he was blasted again out of corporeal existence. For good measure, the grave of his father was exhumed and all the bones utterly destroyed - to prevent a reprise of that particular reincarnation trick.
The remaining Death Eaters were next summoned, using Barty Crouch junior's arm charm, arrested, and sent off to the slammer. The aurors and unspeakables of the Ministry of Magic were ordered to get off their butts and find some Horcruxes. They mostly proved rather easy to locate and identify.