Are you sure you understand what you're asking? An antonym means an opposite, and generally only individual words can have antonyms. But nonetheless: The antonym of "no man is an island" would be "every man is an island." If you're looking for the meaning of the idiom, it means that no one lives their life without being affected by the world around them. Every life is influenced by its surroundings.
Don't call me, I'll call you
Unanimously
Artifact is a man-made object so an antonym would be a manufactured object.
No because you can figure out the meaning. "Picking on" is slang, however, for attacking or teasing.
In this idiom, "letters" refers to the letter abbreviations after the name of a person who has graduated from college. You may see a doctor abbreviated M.D. or someone with an academic doctorate as Ph.D. Thus, a man of letters is someone who has completed a college education and is accomplished.
Don't call me, I'll call you
No it is an island.
Madagascar is not an idiom, it is an island off the coast of Africa.
It means that every man has a degree of interaction and interdependancy with the rest of his surroundings. It would include both fellow man as well as external influences.
The last straw, or the straw that broke the camel's back.
Island
Unanimously
An antonym of bachelor is a husband or a married man
landlocked, mainland
The antonym of peninsula is island. Unlike a peninsula, which is land surrounded by water on three sides, an island is land completely surrounded by water.
simile, metaphor, idiom, personification, hyperbole, alliteration, onomatopoeia.
I would say an antonym could be lapel. As in a flower that a man wears.