Niall Ross

Niall Ross is the former deuteragonist (previously tritagonist) and a survivor of the outbreak in AMC's The Walking Dead. He is the son of Susan Ross and the older brother of Jason Ross. During the initial outbreak, Niall and his mother went to the refuge camp as his brother went and took refuge in the Center for Disease Control during the outbreak, before eventually reuniting with both of them. As time progresses, Niall quickly become hardened due to the environment around him. He was in a relationship with Sophia Peletier before her death, and became depressed because of it. This did, make him toughen up even more than before.

Death
Killed By In order to mark a border between the land belonging to the Whisperers and the communities, Alpha disguises herself and infiltrates the fair to kidnap several residents. Afterward, she decapitates them and then places their heads on wooden pikes to mark the border, with Niall being among them. After finding the border, his zombified head is put down by Carl.
 * Alpha (Alive, Off-Screen)
 * Carl Grimes (Zombified)

Killed Victims
This list shows the victims Niall has killed:
 * Alisha
 * Perry (Indirectly Caused)
 * 10 unnamed Saviors
 * 2 unnamed Whisperers
 * Numerous amount of walkers

Season 1

 * "Days Gone Bye"
 * "Guts"
 * "Tell It to the Frogs"
 * "Vatos"
 * "Wildfire"
 * "TS-19"

Season 2

 * "What Lies Ahead"
 * "Bloodletting"
 * "Save the Last One"
 * "Cherokee Rose"
 * "Chupacabra" (Flashback)
 * "Secrets"
 * "Pretty Much Dead Already"
 * "Nebraska"
 * "Judge, Jury, Executioner"
 * "Better Angels"
 * "Beside the Dying Fire"

Season 3

 * "Seed"
 * "Sick"
 * "Killer Within"
 * "Say the Word"
 * "Hounded"
 * "When the Dead Come Knocking"
 * "Made to Suffer"
 * "The Suicide King"
 * "Home"
 * "I Ain't a Judas"
 * "Clear"
 * "Prey"(No Lines)
 * "This Sorrowful Life"
 * "Welcome to the Tombs"

Season 4

 * "30 Days Without An Accident"
 * "Infected"
 * "Isolation"
 * "Internment"
 * "Dead Weight" (No Lines)
 * "Too Far Gone"
 * "Inmates"
 * "Still"
 * "Us"
 * "A"

Season 5

 * "No Sanctuary"
 * "Strangers"
 * "Four Walls and a Roof" (No Lines)
 * "Crossed"
 * "Coda"
 * "What Happened and What's Going On" (No Lines)
 * "Them"
 * "The Distance"
 * "Remember"
 * "Forget"
 * "Try"
 * "Conquer"

Season 6

 * "First Time Again" (Flashback, No Lines)
 * "JSS"
 * "Now"
 * "Heads Up"
 * "Start to Finish"
 * "No Way Out"
 * "The Next World"
 * "Knots Untie"
 * "Twice as Far"
 * "East"
 * "Last Day on Earth"

Season 7

 * "The Day Will Come When You Won't Be"
 * "Service"
 * "Go Getters"
 * "Sing Me a Song"
 * "Hearts Still Beating"
 * "Rock in the Road"
 * "New Best Friends"
 * "Bury Me Here"
 * "Something They Need"
 * "The First Day of the Rest of Your Life"

Season 8

 * "Mercy"
 * "The Damned"
 * "Monsters"
 * "The King, the Widow, and Rick"
 * "Time for After"
 * "How It's Gotta Be"
 * "Honor"
 * "The Lost and the Plunderers"
 * "Dead or Alive or"
 * "The Key"
 * "Do Not Send Us Astray"
 * "Worth"
 * "Wrath"

Season 9

 * "A New Beginning"
 * "The Bridge"
 * "Warning Signs"
 * "The Obliged"
 * "What Comes After"
 * "Who Are You Now?"
 * "Evolution"
 * "Adaptation"
 * "Omega"
 * "Bounty"
 * "Guardians"
 * "Chokepoint"
 * "The Calm Before"

Trivia

 * Niall lost his virginity to Haley in "Bounty"
 * As of his death in "The Calm Before", Jason is the only surviving blood relative of his family
 * Niall is the last character to die in Season 9.