General:
* Finish
* Terminate
* Conclude
* Cease
* Close
* Stop
* Complete
* Final
* Ultimate
Specific:
* Conclusion (end of a process or argument)
* Termination (end of something that is planned or intended)
* Death (end of life)
* Extinction (end of a species)
* Demise (end of something that is considered important)
* Expiry (end of a period of time)
Figurative:
* Culmination (highest point or final stage)
* Apex (highest point)
* Climax (most intense point)
* Denouement (resolution of a story)
In a sentence:
* "The end of the story was very sad." (general)
* "The meeting will terminate at 5:00 PM." (specific)
* "He reached the climax of his career." (figurative)
The best synonym for "end" will depend on the specific context in which you are using it.