Graystripe returns in The Sight.
Scourge dies in the 6th book of the Original Arc 'The Darkest Hour'.
In the series warriors by Erin hunter I would have to say there is more than one but I'l list them Forest of secerets, series 1, Silverstream dies A dangerous path, series 1, Bluestar, swiftpaw, die and brightheart badly indured Twillight, series 2, Cinderpelt and sootfur die and all cats of thunderclan badly indured sunrise, hollyleaf tells all the clans leafpool's secert,brambleclaw is mad leafpool leaves thunderclan hollyleaf dies
Yes, she dies in The Forest of Secrets, which is the first book of the first series, bearing Graystripe's kits.
Birdflight does not die in a book, but she dies.
Yes she dies in the third book of the Omen Of The Stars book. It is hinted within the series that she is growing older and weaker, Mistystar takes her place
Heathertail, a character from the Warriors book series, died during a battle in the book "Night Whispers." She was fatally wounded by a falling tree.
Moonrise
he turns into a aprentice in outcast but im not sure if he does
In the Warriors book series, Dovewing does not die. She survives through the end of the main arc and plays important roles in various storylines.
Sandstorm dies in the Warriors series in the book "The Last Hope" during the battle against the Dark Forest. She sacrifices herself to save Firestar from a fatal attack.
Spiderleg did not die yet in the series.
The Erins have not revealed the book that Brambleclaw will die in, probably in the battle with the Dark Forest.