I’m going with William Windom:
https://www.youtube.com/watch?v=lS7cK-mQ0fQ&t=134s
Staving off reality:
https://www.youtube.com/watch?v=qmnpz6TheSs
Doing a villain turn by seizing control:
https://www.youtube.com/watch?v=83tW0jhEvZE
Matt’s heroic sacrifice:
https://www.youtube.com/watch?v=U_mwtoeqneM
Finally, one of the most nail-biting scenes ever:
https://www.youtube.com/watch?v=DHmsnQ8WVpw
Personal notes: across all TV and media, I’ve rarely seen a character go from totally sympathetic, to total heel-turn villain, to total martyr like that.
In terms of ST series, maybe Dukat from DS…?
Runner-ups?
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Mark Lenard as the Romulan commander
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Robert Walker as “Charlie X”
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Roger C. Carmel as “Harry Mudd”
Daggit, I know I’m forgetting some actors, here…
Excluding the obvious choice of Jeffrey Combs as… well anyone really, I’m rather fond of Andreas Katsulas, though I may be partial to him for his phenomenal role as G’Kar on Babylon 5.
Sadly not TOS T.T
I haven’t seen all of them yet (half way through season 2) but right now I’d say
William Campbell
In … The Squire of Gothos … and also appeared as Klingon Captain Koloth
His acting and persona is equal parts lovable and hateable … the kind of guy you could be friends with while also wanting to stay away from as much as possible.
The other guest actor that I felt the same about was
Roger C. Carmel
In … Mudd’s Women … and later in … I, Mudd
William Campbell is my favorite, too. His characters were all so over the top.
TNG spoilers:
Spoiler
Hey, was he one of the Q? Just never revealing himself?! Playing with this great starship captain for amusement.
Not going to state the obvious with Ricardo Montalban, but I always enjoyed William Campbell’s Trelaine. And yeah, Windom was solid as Decker. Great episode all around.
Was expecting the title to end with “, and why is it William Windon?” before I read the second half of the sentence 🤣
