We're not ready to say goodbye.
Practically no one is safe in the latest Arrow-verse crossover--regardless of how significant a character they are in DC Comics mythology. Crisis on Infinite Earths, thus far, has killed off a version of Bruce Wayne (Kevin Conroy), as well as the Green Arrow (Stephen Amell). Of course, it remains to be seen how permanent the Green Arrow's death is. Warning: The following contains spoilers for the third installment of the Crisis on Infinite Earths crossover. If you have yet to see it, stop reading now.
Now, you can add The Flash to the list. No, the Barry Allen (Grant Gustin) you tune in to watch every week on The CW isn't dead. Instead, it was the Barry Allen of Earth-90, played by John Wesley Shipp. For those having trouble keeping track of the infinite Earths of the Arrow-verse, that's the same Flash from the 1990s TV series.
All this season, the Monitor (LaMonica Garrett) has told Barry (Gustin) that the Flash had to die during the Crisis. At no point did he think it was possible that the Flash in question was one from another Earth. In the third episode of the crossover, though, viewers saw that prophecy come to pass as Earth-90's Flash disintegrated while trying to stop the wave of anti-matter from destroying Earth-1--which ultimately proved futile.
Still, with his demise, The CW paid tribute to the original Flash TV series by flashing back to a memory of the elder Barry's, in which he shares a tender moment with Tina (Amanda Pays), the character's love interest on the show.
In the end, with Earth-90's Flash dead and the entirety of the multiverse destroyed, a handful of heroes were sent to the Vanishing Point to figure out how to reverse everything that's been unleashed.
In the comics, the Vanishing Point is a dimension that exists outside of the time/space continuum, meaning the anti-matter wave that killed off the various Earths did not harm it.
How those who survive--The Flash (Gustin), Supergirl (Melissa Benoist), Batwoman (Ruby Rose), Ryan Choi (Osric Chau), Sara Lance (Caity Lotz), J'onn J'onzz (David Harewood), and Lex Luthor (Jon Cryer)--will save the multiverse or any of the people that have been wiped out of existence is anyone's guess. Another mystery is what happened to Superman (Brandon Routh), who also went to the Vanishing Point before he was replaced with Lex.
These are questions that won't get answered until January 14, when the final two installments in the Crisis on Infinite Earths crossover air on The CW.