This story contains spoilers for “Crisis on Infinite Earths: Part 1 and 2,” aka Supergirl Season 5, Episode 9 and Batwoman Season 1, Episode 9.
The Arrowverse’s fearless leader, Oliver Queen, died during “Crisis on Infinite Earths Part 1.” His death came as quite a shock to both his daughter Mia, his fellow heroes, and likely plenty of viewers at home who were watching the Crisis unfold. Oliver sacrificed his life to save billions of people on Kara’s world of Earth-38, just as the anti-matter wave consumed the planet. The Monitor was able to bring Oliver’s body back to Earth-1, but he didn’t survive the battle.
Source: IGN.com Crisis on Infinite Earths Resurrects the Lazarus Pit to Save [Spoiler]