Imprisoned in an apartment with a complete stranger, an idealist twenty-something has to find a way to save herself and the world population from the secret organization holding her captive.

"When a secret organization launches the last step of its plan to eliminate 99% of the population, one of its main agent abducts his estranged humanitarian daughter so she can live in the new society."

Since this isn't the main logline, one used to sell the script, it is fine because it shows you understand the goal and motivation of the antagonist. If you still want to revise it for practice, what is the last step? Be more specific, whether it's poison like I used in my example or something, being more specific would probably shorten the logline.

Now, onto the main logline. It seems that you haven't posted a revision. So, for:

"Imprisoned in an apartment with a complete stranger, an idealist twenty-something has to find a way to save herself and the world population from the secret organization holding her captive."

You have an inciting incident(abduction), which is clear. Now, what do you see as the goal? Due to her being abducted by her estranged father, what does this motivate her to do? Is her goal to stop them after she finds out what they plan to do?

>>>And also, she?s an idealist and wants to make a better world which means that, even though she might not understand it at first, starting over could be doing just that.

So what's her character arc? ?The focus of ?a logline ?is the through line of the action toward an object goal (which, in her case is?), but in delineating a through line it should suggest a character arc that the protagonist undergoes along the way.

By the end of the story how we will she differ from what she was at the start?

" When his secret organization?s plan to recolonize Earth is unfolding, an estranged father attempts to include his humanitarian/idealist daughter in the plan."

A logline framed around an antagonist should still include the same elements. It should have an inciting incident, whether it's different from the protagonist's, or in some cases it could be the same event. But for the antagonist it could be something which happens offscreen. So what single, specific event causes him to kidnap his daughter?

Also, describe the father using his occupation or skills, or a personality trait.

Example:?When his secret organization releases a biochemical which will eliminate a majority of the human population, an agent abducts his estranged humanitarian daughter so she can live?in the new society. (31)

?If you've seen The Dark Knight, here's a video?from a great channel analyzing what makes a good antagonist. I've found Lessons From the Screenplay to be a great, insightful resource for better understanding storytelling.?