The Battle of Tumbleton is remembered for several major deaths, but the best- known one is Prince Daeron Targaryen, whose death is described in conflicting ways in the source material. Other key figures who die there include Addam of Hull, Hugh Hammer, Ulf White, and dragons such as Tessarion, Vermithor, and Seasmoke.
First Battle
In the First Battle of Tumbleton, Lord Ormund Hightower is killed during the fighting. The accounts also describe Ser Bryndon Hightower dying with him, while the battle itself turns into a chaotic Green victory that leaves the town devastated.
Second Battle
The Second Battle of Tumbleton is even bloodier. Addam of Hull dies in the fighting, and Prince Daeron Targaryen is also killed, though the exact manner of his death is not settled in the text. Hugh Hammer dies there as well, and Ulf White is murdered amid the betrayal and violence around the battle.
Dragons and fallout
The battle is also famous for the deaths of major dragons. Tessarion, Vermithor, and Seasmoke all die in the clash, making Tumbleton one of the most destructive dragon battles in the Dance of the Dragons. If you want the shortest answer: the major people who died at Tumbleton were Ormund Hightower, Bryndon Hightower, Addam of Hull, Hugh Hammer, Ulf White, and Prince Daeron Targaryen, along with several dragons.