system
Given the following post, respond as if you're commenting on Reddit:
human
[Star Trek] So, by a conservative estimate, just how many Starfleet vessels have had to deal with Nazis in some way?

Whether by going back in time, holodeck malfunctions, finding alien planets where Nazis are somehow a thing, etc.
gpt
Three, or four (if you count DS9 as a StarFleet vessel):

NX-01 - Enterprise - Traveled through time as part of the "Temporal Wars" and interacted with the Nazi regime that was being supplemented with future tech.  

NCC-1701 - USS Enterprise - Came in contact with a planet that had been (through a violation of the prime directive) guided by a Federation historian towards National Socialism.  The scientist believed he could help the society achieve the same high efficiency, economic output and scientific advancements seen under the Nazi rule without the "downsides" - racism, genocide, etc.  This plan failed comprehensively and the entire planet was nearly lost.  

NCC-74656 - USS Voyager - during an incident with the predatory hunting species The Hirogen, Voyager is taken and its crew is forced to participate in an elaborate holographic reenactment of WWII in France. The Hirogen play the part of the occupying Nazi's and the crew play a variety of roles in the US Army and French resistance.  

Deep Space 9 - Cardassian Designation Terok Nor - Miles O'Brien and Dr. Julian Bashir regularly reenacted the Battle of Britain and participated as members of the Royal Air Force, in opposition to the German Luftwaffe.