First pick! I'll save Phage then, as the Vidiians were one of VOY's most creative enemies. They looked pretty scary, and yet they were also quite tragic. They find themselves acting out of desperation and harvesting organs because they were all infected with the Phage.
TOS #4: "The Naked Time"
TOS #7: "What Are Little Girls Made Of?"
TAS #4: "The Lorelei Signal"
TAS #7: "The Infinite Vulcan"
TNG #4: "The Last Outpost"
TNG #7: "Justice"
DS9 #4: "Babel"
DS9 #7: "Dax"
VOY #7: "Ex Post Facto"
ENT #4: "Unexpected"
ENT #7: "Breaking The Ice"
DIS #4: "The Butcher's Knife Cares Not For The Lamb's Cry"
DIS #7: "Magic To Make The Sanest Man Go Mad"
ST #4: "The Escape Artist"
ST #7: "Ask Not"
PIC #4: "Absolute Candor"
PIC #7: "Nepenthe"
LD #4: "Moist Vessel"
LD #7: "Much Ado About Boimler"
PRO #4: "Terror Firma"
PRO #7: "Time Amok"
Movie #4: "Star Trek IV: The Voyage Home"
Movie #7: "Star Trek Generations"
TOS #4: "The Naked Time"
TOS #7: "What Are Little Girls Made Of?"
TAS #4: "The Lorelei Signal"
TAS #7: "The Infinite Vulcan"
TNG #4: "The Last Outpost"
TNG #7: "Justice"
DS9 #4: "Babel"
DS9 #7: "Dax"
VOY #7: "Ex Post Facto"
ENT #4: "Unexpected"
ENT #7: "Breaking The Ice"
DIS #4: "The Butcher's Knife Cares Not For The Lamb's Cry"
DIS #7: "Magic To Make The Sanest Man Go Mad"
ST #4: "The Escape Artist"
ST #7: "Ask Not"
PIC #4: "Absolute Candor"
PIC #7: "Nepenthe"
LD #4: "Moist Vessel"
LD #7: "Much Ado About Boimler"
PRO #4: "Terror Firma"
PRO #7: "Time Amok"
Movie #4: "Star Trek IV: The Voyage Home"
Movie #7: "Star Trek Generations"