* Cedric Diggory: The champion of Hogwarts, Cedric is killed by Peter Pettigrew (Wormtail) at the end of the Triwizard Tournament. This death deeply impacts Harry and the wizarding world.
* Frank Bryce: An old gardener who was a neighbor of the Riddle family and is killed by Peter Pettigrew at the beginning of the book. He is initially thought to be a victim of the Dark Mark, but Harry discovers his true killer later.
While not strictly *death*, we can also consider:
* Barty Crouch Jr.: The son of the Minister of Magic is disguised as Alastor "Mad-Eye" Moody and eventually dies from the effects of the Imperius Curse.
* Dobby: While not in Goblet of Fire, Dobby's death in Harry Potter and the Deathly Hallows is a direct result of events that happened in Goblet of Fire (saving Harry from being sent back to the Dursleys by breaking the Triwizard Cup).