I always liked the Melkot in "Spectre of the Gun". They're pretty blunt about their feelings, even posting a clearly understood No Trespassing sign, unlike Balok of the First Federation, who uses deception.
Aliens! You have encroached on the space of the Melkot. You will turn back immediately. This is the only warning you will receive.
Translation: "Hey you! Get off my lawn. I ain't gonna tell ya again."
Kirk and party are again addressed as aliens, outsiders, and a contamination when they seem to meet a Melkot face to face. And since the patterns of their deaths are taken from Kirk's mind, the setting, the actions, and even the confrontations with the Sheriff and the Earps are like something out of an old west movie.
KIRK: . . .We don't want any trouble.
MORGAN: If you don't want any trouble, what are you doing in my town?
When the crew finally finds a way out of the situation without killing the Earps, only then do the Melkot address Kirk by name.
The best thing about them is although their level of xenophobia has been seen in other species, these are definitely non-humanoid creatures for a change.