That would be 'introduction'.
An antonym for the word "inception" is "conclusion" or "ending."
Conclusion.
end, conclusion
conclusion, treaty, agreement
The antonym of climax is anti-climax, which refers to a disappointing or unexciting conclusion to a series of events or a story.
End, omega, conclusion, termination are all antonyms of beginning
end, conclusion, finish, conclude, complete and stop
You may be confusing foreword with the soundalike forward. As an adverb it refers to a direction towards the front of something (facing forward); its antonym would be backward.
With the sense of point for discussion, debate, analysis, writing or presentation, the word topic does not have an antonym. Not every word has an antonym. Most books have titles. The word title does not have an opposite. The word carbon does not have an opposite. Many words can evoke other words that are unlike them, but unlike does not mean opposite. Some may jump to the conclusion that 'hot dog' is the antonym of 'hamburger'. They are not opposites; they are different.
The antonym of the word 'synonym' is 'antonym'.
An antonym means "opposite". So an antonym for the word synonym is antonym.
The antonym for from is to. Because antonym means opposite.