JD reviewed the first half for Bureau 42 here.  The second half actually has action, tragedy, status-quo changes, everything a major event is supposed to have.

Title: “Crisis on Earth X, Parts Three and Four”

Cast and Crew
Directors: Dermott Daniel Downs, Gregory Smith
Writers: Todd Helbing, Phil Klemmer, Keto Shimizu, Andrew Kreisberg, Marc Guggenheim

Grant Gustin as Barry Allen / The Flash
Candice Patton as Iris West
Victor Garber as Dr. Martin Stein
Emily Bett Rickards as Felicity Smoak / Jewish Prisoner
Caity Lotz as Sara Lance / White Canary
Chyler Leigh as Alex Danvers
Paul Blackthorne as Sturmbannführer
Franz Drameh as Jefferson Jackson / Firestorm
Jeremy Jordan as Winn Schott
Juliana Harkavy as Dinah Drake / Black Canary
Wentworth Miller as Leo Snart / Citizen Cold
Russell Tovey as Ray Terrill / The Ray
Brian Cook as Nazi
Frederick Schmidt as Metallo-X (voice)
Brett Alexander Davidson as Nazi Facility Guard (as Brett Davidson)
Brandon Routh as Ray Palmer / The Atom
Maisie Richardson-Sellers as Amaya Jiwe / Vixen
Amy Louise Pemberton as Gideon (voice)
Tala Ashe as Zari Tomaz
Nick Zano as Nate Heywood / Steel
Dominic Purcell as Mick Rory
Stephen Amell as Oliver Queen / Green Arrow / Dark Arrow
David Ramsey as John Diggle
Tom Cavanagh as Dr. Harry Wells / Eobard Thawne / Dark Flash
Chyler Leigh as Alex Danvers
Danielle Panabaker as Caitlin Snow / Killer Frost
Carlos Valdes as Cisco Ramon / Vibe
Echo Kellum as Curtis Holt / Mr. Terrific
Melissa Benoist as Kara Danvers / Supergirl / Overgirl
Rick Gonzalez as Rene Ramirez / Wild Dog
Juliana Harkavy as Dinah Drake / Black Canary
Wentworth Miller as Leo Snart / Citizen Cold
Russell Tovey as Ray Terrill / The Ray
Christina Brucato as Lily Stein
Isabella Hofmann as Clarissa Stein
Charles Zuckermann as Nazi Commander
Adam Klassen as Nazi Navigator

Premise

The heroes find themselves trapped on Earth-X, and have to stop the most evil of heart transplants.  Once free, the final battle happens on Earth 1, followed by some stirring emotional moments.

High Points

We see lasting changes for characters, and the emotional resonance hit pretty solidly (both the good and the sad.)

We see the level of battle that we expect from a show with this many heroes.

The “subtle” change to Snart for his doppelganger was entertaining.

Low Points

Eobard’s exit.  I could not reconcile this decision with any form off sound reasoning, comic book or otherwise.

Per a guess from the comments earlier on this site, I was hoping that Lucifer was going to find a way to have a cameo, but the devil was not in the details.

The Scores:

Originality: 3/6 They weren’t as heavily telegraphed as they were for the first two parts, but we still don’t find anything groundbreaking.

Effects: 4/6 The effects budget was significantly stretched, and it showed with CGI people who looked as rubbery as the early aughts.

Acting: 6/6 They called for some strong performances from the cast, and the cast delivered.

Story: 3/6 The story isn’t bad, but many things happen purely because the characters need to be somewhere else after this story ends.  Also, the pacing is a bit derailed with the sad character moments before the ultimate battle.

Emotional Response: 6/6 We laughed at the jokes, my wife wept at the appropriate points, they hit all the points.

Production: 5/6  They did a good job of having four different shows blend and mix, even getting better at having a reason that supporting characters weren’t present.

Overall: 5/6 In total, “Crisis on Earth X: Part Three and Part Four” receives 32/42