In 2374 the Krenim scientist Annorax used a temporal weapon ship to rewrite history, nearly destroying Voyager before the timeline was restored.
In 2374 Voyager entered space claimed by the Krenim. The scientist Annorax commanded a weapon ship that could erase entire species from history, and he had spent two centuries trying to restore the Krenim Imperium and bring back his wife, who had been lost through one of his own changes.
Voyager was battered for months, and most of the crew left the ship while Chakotay and Paris were held aboard the weapon ship. Janeway rammed the weapon ship with Voyager, wiping it from history and resetting the timeline so that none of it happened.