The Arrowverse had seven major crossovers during its run on The CW, but only one does enough to be considered the best.

Though the publisher has had several crossovers and events since then, no event has been more influential on DC Comics than Crisis on ... version of The Flash traveled from Earth-One to Earth ...

The third and final installment in the animated Justice League: Crisis ... and Earth-2 Superman; Stana Katic as Wonder Woman and Superwoman; Jensen Ackles as Batman; Matt Bomer as The Flash ...