Does it make sense?
A bitter ending is better than bitterness without ending.

is there a better word to be used instead of bitter and bitterness like sad...?

For your information this is a dialogue from an Iranian movie called "about elly".

Question

Does it make sense?
A bitter ending is better than bitterness without ending.

is there a better word to be used instead of bitter and bitterness like sad...?

For your information this is a dialogue from an Iranian movie called "about elly".

Answer

Bitter and bitterness are better here because they suggest pain and hardship, rather than just sorrow.  I would guess that this is what the writer wants to say.

A very common English saying is:

'[to do something] to the bitter end'.

Answer

You could say: A bitter ending is better than long lasting  hostility/resentment.

Answer

Very poetic.