The superheroes of The Flash, Arrow, Supergirl and DC's Legends of Tomorrow couldn't fight their evil Nazi doppelgangers from Earth-X without there being casualties. It would certainly be expected that a full-on invasion of Earth-1 by Nazis would result in lots of deaths, but some fans were understandably shocked at how bloody Crisis On Earth-X actually was.
The four-hour Arrowverse crossover event saw Earth-1's Central City under attack by the Earth-X Nazi Schutzstaffel. In the final battle, numerous innocent citizens and Central City Police officers in the Nazis' path were cut down before the superheroes arrived to do battle. There was also no sparing the lives of Nazi soldiers throughout the crossover. Plenty of Nazis were killed by the heroes in the course of several eye-popping super fights between the heroes and villains. Even the wedding of Barry Allen (Grant Gustin) and Iris West (Candice Patton) was interrupted by their priest being killed when the Nazis invaded the church.
Here are the major characters, a few of whom were big surprises, who lost their lives in Crisis On Earth-X:
Earth-X's James Olsen
The first casualty of the crossover was the James Olsen (Mehcad Brooks) of Earth-X. In the guise of the Guardian (with a shield adorned with the stars and stripes of the flag of the defunct USA), James failed to stop the Oliver Queen of Earth-X (Stephen Amell) from taking the dimensional transporter of the Freedom Fighters. After a brief fight, Oliver murdered James before securing the transporter, not fearing James' dying promise that there were others like him who would try to stop him.
Earth-X's Tommy Merlyn
Wearing the hood of Prometheus, Tommy Merlyn (Colin Donnell) was captured at Barry and Iris' wedding after being taken down by Sara Lance (Caity Lotz) and Alex Danvers (Chyler Leigh). Tommy was imprisoned in the Pipeline beneath STAR Labs and offered Earth-1's Oliver some background on what life is like on Earth-X before he committed suicide via cyanide.
Earth-1's Tommy was Oliver's best friend and the same held true for Oliver and Tommy on Earth-X. Tommy was Arrow's first major death when Tommy died during the Undertaking in the season 1 finale. Tommy briefly reappeared as a vision in the 100th episode of Arrow during last year's Invasion crossover. With Tommy unexpectedly returning once more in Crisis on Earth-X, it's now becoming a fun tradition for Colin Donnell to reappear during the annual Arrowverse crossovers.
Earth-X's Red Tornado
The Earth-X Freedom Fighters had a Red Tornado android of their own, which they deployed to destroy the interdimensional gateway to Earth-1. The Flash and the Ray (Russell Tovey) raced to stop the Tornado, as their own teammates were still fighting to secure the gateway from the Nazis. Together, Flash and Ray managed to destroy the Red Tornado by combining their powers into a lightning bolt attack.
Supergirl (Melissa Benoist) fought a rogue Red Tornado in season 1 of her titular series, but the Earth-X version looked to be a much more sophisticated and improved design than the one the Girl of Steel ultimately destroyed.
The Schutzstaffel deployed their own Metallo when the heroes were beaten by Overgirl, the Dark Flash (Tom Cavanagh) and the Nazis at the end of the second hour. Metallo's Kryptonite heart and energy blasts prevented Supergirl from escaping STAR Labs when Iris West and Felicity Smoak (Emily Bett Rickards) tried to rescue her. In the end, the combined powers of Cisco Ramon (Carlos Valdes), Black Canary (Juliana Harkavy), Firestorm (Franz Drameh), Team Arrow and the Legends of Tomorrow overwhelmed and destroyed Metallo.
Supergirl and her cousin Superman (Tyler Hoechlin) faced two Metallos in season 2 of Supergirl, needing the help of the Martian Manhunter (David Harewood) and Alex Danvers to ultimately prevail. The Earth-X version of Metallo is a robot, compared to the cyborg Metallos found on Earth-38, but was no less equipped with a Kryptonite heart.