Enemy would be the opposite of friendship. Friendship is when you like and care about each other, and want each other to do well. The exact opposite is true of enemies.
One word that means the opposite of disgusting is attractive.
One such word would be whisper.
One! Several means two or more, but not many
One possibility is disposable.
One is shutting.
You have to specify what "this one' is.
One word would be "immaculate" (spotlessly clean).
Cluster means a close grouping of things, so yes it would be considered an antonym. Words it is opposite of would be: one, singular, etc.
The prefix "in" means "the opposite of", so "inexhaustible" means the same as "not exhaustible". One word is the exact opposite of the other.
The word Anonymous means to do something and no one knows who did it. The word antonym means a word that is the opposite. So the antonym for approve would be disapprove.
A word that has five syllables that means friendship is accompaniment (ac-com-pa-ni-ment). A sentence that means friendship that is five syllables is "friendly relation" or "state of being friends".
Hypocrisy means saying one thing or holding a belief, and doing the opposite. The opposite of hypocrisy is honesty, straightforwardness, and sincerity.