For suddenness:
* Abrupt termination: This is a formal way to say "abrupt end."
* Sudden demise: This implies an unexpected and often unfortunate end.
* Precipitous end: This suggests a rapid and steep descent.
For unexpectedness:
* Unexpected conclusion: This emphasizes the element of surprise.
* Untimely end: This implies that the end came before its natural time.
For finality:
* Finality: This word itself conveys a sense of absolute conclusion.
* Conclusion: This is a more neutral term, but can still imply finality.
For negative connotations:
* Cut short: This suggests that something was ended prematurely.
* Truncated: This implies that something was shortened in an unnatural way.
* Cutoff: This emphasizes a sudden and decisive ending.
For specific scenarios:
* Closure: For the end of a relationship or project.
* Termination: For the end of employment or a contract.
* Cancellation: For the end of an event or plan.
The best word to use will depend on the specific context and the feeling you want to evoke.