I think Osyraa was a much better villain than she's given credit for. Our first real insight into the smart and scheming Orion matriarchy. Before Lower Decks came along she was the best example of how Orion women control their society without needing to use sexual manipulation. Her diplomatic games with Vance were great.
Gary Seven (TOS S2, "Assignment: Earth")
The Cold War (TOS S2, "Assignment: Earth")
Janice Lester (TOS S3, "Turnabout Intruder")
The Skorr (TAS S1, "The Jihad")
Backwards Time Universe (TAS S2, "The Counter-Clock Incident")
Commander Tebok & Sub-Commander Thei (TNG S1, "The Neutral Zone")
Predatory Vines of Surata IV (TNG S2, "Shades Of Grey")
Devidians (TNG S5, "Time's Arrow")
Lore (TNG S6, "Descent")
Neela (DS9 S1, "In The Hands Of The Prophets")
Talak'talan (DS9 S2, "The Jem'Hadar")
Eris (DS9 S2, "The Jem'Hadar")
Krajensky Shapeshifter (DS9 S3, "The Adversary")
Pah-Wraiths (DS9 S6 & S7, "Tears Of The Prophets", "What You Leave Behind")
The Dominion War (DS9 S5, S6, & S7, "Call To Arms", "Tears Of The Prophets", "What You Leave Behind")
Cheese (VOY S1, "Learning Curve")
Culluh (VOY S2, "Basics")
Species 8472 (VOY S3, "Scorpion")
Captain Ransom (VOY S5, "Equinox")
Borg Queen (VOY S6 & S7, "Unimatrix Zero" and "Endgame" & PIC S3 "The Last Generation")
Silik (ENT S1, "Shockwave")
Future Guy (ENT S1, "Shockwave")
Duras (ENT S2, "The Expanse")
The Xindi (ENT S2, "The Expanse")
Dolim (ENT S3, "Zero Hour")
The Sphere Builders (ENT S3, "Zero Hour")
Na'kuhl Nazi (ENT S3, "Zero Hour")
Off-Camera Admiral Pressman (ENT S4, "These Are The Voyages...")
Holographic Recreation Of Unnamed Alien Criminal (ENT S4, "These Are The Voyages...")
Emperor Georgiou (DIS S1, "Will You Take My Hand?")
The Klingon War (DIS S1, "Will You Take My Hand?")
Control (DIS S2, "Such Sweet Sorrow, Part 2")
Species 10-C (DIS S4, "Coming Home")
Moll (DIS S5, "Life, Itself")
Primarch Tahal & The Breen (DIS S5, "Life, Itself")
Oh (PIC S1, "Et In Arcadia Ego, Part 2")
Narissa (PIC S1, "Et In Arcadia Ego, Part 2")
Sutra (PIC S1, "Et In Arcadia Ego, Part 2")
Genocidal Alliance Of Synthetic Life From Beyond Time And Space (PIC S1, "Et In Arcadia Ego, Part 2")
Adam Soong (PIC S2, "Farewell")
Destructive Fissures, Triquantum & Regular Quantum Varieties (PIC S2, "Farewell" & LD S5, "The New Next Generation")
Solar Flares (LD S2, "First First Contact")
Admiral Buenamigo (LD S3, "The Stars At Night")
The USS Aledo and the Texas Class Fleet (LD S3, "The Stars At Night")
D'Erika (LD S4, "Old Friends, New Planets")
Relga (LD S5, "The New Next Generation")
The Living Construct (PRO S1, "Supernova, Part 2")
Ascensia (PRO, S2, "Ouroboros, Part II")
The Loom (PRO S2, "Ouroboros, Part II")
The Romulan Praetor (SNW S1, "A Quality Of Mercy")
Pike's Efforts To Avoid The Beep Chair Destroying The Future (SNW S1, "A Quality Of Mercy")
Discriminatory Laws Against The Genetically Modified (SNW S1, "A Quality Of Mercy")
The Gorn (SNW S2, "Hegemony")
Gary Seven (TOS S2, "Assignment: Earth")
The Cold War (TOS S2, "Assignment: Earth")
Janice Lester (TOS S3, "Turnabout Intruder")
The Skorr (TAS S1, "The Jihad")
Backwards Time Universe (TAS S2, "The Counter-Clock Incident")
Commander Tebok & Sub-Commander Thei (TNG S1, "The Neutral Zone")
Predatory Vines of Surata IV (TNG S2, "Shades Of Grey")
Devidians (TNG S5, "Time's Arrow")
Lore (TNG S6, "Descent")
Neela (DS9 S1, "In The Hands Of The Prophets")
Talak'talan (DS9 S2, "The Jem'Hadar")
Eris (DS9 S2, "The Jem'Hadar")
Krajensky Shapeshifter (DS9 S3, "The Adversary")
Pah-Wraiths (DS9 S6 & S7, "Tears Of The Prophets", "What You Leave Behind")
The Dominion War (DS9 S5, S6, & S7, "Call To Arms", "Tears Of The Prophets", "What You Leave Behind")
Cheese (VOY S1, "Learning Curve")
Culluh (VOY S2, "Basics")
Species 8472 (VOY S3, "Scorpion")
Captain Ransom (VOY S5, "Equinox")
Borg Queen (VOY S6 & S7, "Unimatrix Zero" and "Endgame" & PIC S3 "The Last Generation")
Silik (ENT S1, "Shockwave")
Future Guy (ENT S1, "Shockwave")
Duras (ENT S2, "The Expanse")
The Xindi (ENT S2, "The Expanse")
Dolim (ENT S3, "Zero Hour")
The Sphere Builders (ENT S3, "Zero Hour")
Na'kuhl Nazi (ENT S3, "Zero Hour")
Off-Camera Admiral Pressman (ENT S4, "These Are The Voyages...")
Holographic Recreation Of Unnamed Alien Criminal (ENT S4, "These Are The Voyages...")
Emperor Georgiou (DIS S1, "Will You Take My Hand?")
The Klingon War (DIS S1, "Will You Take My Hand?")
Control (DIS S2, "Such Sweet Sorrow, Part 2")
Species 10-C (DIS S4, "Coming Home")
Moll (DIS S5, "Life, Itself")
Primarch Tahal & The Breen (DIS S5, "Life, Itself")
Oh (PIC S1, "Et In Arcadia Ego, Part 2")
Narissa (PIC S1, "Et In Arcadia Ego, Part 2")
Sutra (PIC S1, "Et In Arcadia Ego, Part 2")
Genocidal Alliance Of Synthetic Life From Beyond Time And Space (PIC S1, "Et In Arcadia Ego, Part 2")
Adam Soong (PIC S2, "Farewell")
Destructive Fissures, Triquantum & Regular Quantum Varieties (PIC S2, "Farewell" & LD S5, "The New Next Generation")
Solar Flares (LD S2, "First First Contact")
Admiral Buenamigo (LD S3, "The Stars At Night")
The USS Aledo and the Texas Class Fleet (LD S3, "The Stars At Night")
D'Erika (LD S4, "Old Friends, New Planets")
Relga (LD S5, "The New Next Generation")
The Living Construct (PRO S1, "Supernova, Part 2")
Ascensia (PRO, S2, "Ouroboros, Part II")
The Loom (PRO S2, "Ouroboros, Part II")
The Romulan Praetor (SNW S1, "A Quality Of Mercy")
Pike's Efforts To Avoid The Beep Chair Destroying The Future (SNW S1, "A Quality Of Mercy")
Discriminatory Laws Against The Genetically Modified (SNW S1, "A Quality Of Mercy")
The Gorn (SNW S2, "Hegemony")