A possible antonym of serf could be "free person" or "freeman," as a serf is a person who is bound to the land and essentially owned by a lord, whereas a free person has autonomy and is not bound to servitude.
The antonym of borough is wilderness.
Disobey is an antonym of obey.
Sociologist does not have a direct antonym.
Synonym: Whine Antonym : Compliment
An antonym of bachelor is a husband or a married man
A vassal is a serf or peon. The opposite of that would be the ruler. You could say the lord or lady. You might also say the one in charge.
Whats serf
The homonym for "serf" is "surf."
Your question is not entirely correct in its premise; a serf is not a slave and does not have an owner. A serf is a subject of a land owner whom the serf would address as lord.
In a feudal system, a serf would remain a serf no matter how hard they were to work.
Saint Serf died in 583.
Saint Serf was born in 500.
Riddle answer: a serf board.
Peasant/serf
The noble executed the serf.
I doubt that they thought about the serf one way or the other. The serf was to do the work and didn't require much thought from his master.
Feudal serf attached to the soil is an adscript.