Victor was the father of Valerie Malone. He only appeared via old home movies and in dream and flashback sequences, but his character was the major reason for Valerie's dysfunction throughout the series.
Originally a friend of Jim and Cindy Walsh, they lived near the Walsh family in Minnesota before relocating to Buffalo. After they arrived in Buffalo, Victor began molesting Valerie. In between seasons 4 & 5, Jim and Cindy got a call from Abby stating that Victor had killed himself. However, this was later retconned.
It was explained later that after Tom Miller discovered Valerie's abuse at Victor's hands, he threatened to go to the police if Valerie didn't. When Valerie confronted Victor, they struggled and Valerie killed Victor.
During her last episode, Valerie is wanting to confess to the police, but she is talked out of it by Matt Durning and Abby Malone. Valerie, having dealt with her father's long-standing effect on her life, returned to Buffalo with her mother at the beginning of Season 9.
Victor is incorrectly credited in his episodes as Peter Malone, but dialogue throughout the series indicates that his name was, in fact, Victor.