I rank this the worst TOS episode in the series run, and a contender for the top 10 worst ST episodes overall. Yes, there’s potential for an interesting story there, but it certainly whiffs the execution. The plot holes are enormous and it just makes no sense - I mean, why does anti-matter Lazarus not destroy everything in the matter universe he touches when it’s already been established at least once earlier in the series that matter and anti-matter go kaboom? They try and hand-wave it away but it’s just silly, as is the idea that both universes would be destroyed. Raising the stakes much! And switching requires Lazarus’ ship, yet he doesn’t? I, uh, it’s just all over the place and needed at least another one or two script passes. It also annoyed me how this highly suspicious character is basically allowed to wander the ship.
But it doesn’t matter when set against its failure of execution. Terrible direction, acting, set design and special effects - even by the series standards - make it borderline unwatchable at times. The guy they wanted to play Lazarus left the production, and his replacement doesn’t quite seem to know what to do with the role (understandably as he had no time to prepare for it). His infinitely variable facial hair was the source of some amusement, as was the “oh no, not again!” shot of him falling off that damn cliff with the same canned “arrgh!” sound effect. And the dimensional effects are enough to need an epilepsy warning in those who don’t suffer from it.
The story behind why this was such as disaster is far more interesting than the episode itself, which feels more like one of those early YouTube fan-fiction Star Trek videos where they somehow went back in time to get the real cast to play their roles.