when the greedy powers attempt to get rid of excess population, unruly space peacemaker in civilian mission on earth again must break all the rules and save the human race and the human woman he loves.

Thank you for your comment.
Sci-Fi story is a difficult to explain in 25-35 words. This is my point of view on my logline:
PROTAGONIST- unruly space peacemaker ( He rather break the rules, then obey them, this is the reason why he was sent on earth - to calm down )
ANTAGONIST- greedy powers ( you cannot tell everything in 25-35 words, greedy powers is a well known secret organization which want to reduce human population to a Golden billion, that means other 6 billion is excess or surplus )
GOAL- stop planetary genocide ( my hero is well known as a character who "break all the rules" that means he will do it again although he was sent on earth to "calm down" - that means he will do everything- all dirty tricks, to stop the genocide )
STAKES- billions of people ( hero is on mission on earth, logically he met human woman and he fall in love with her and, logically she is in the 6 billion surplus earth population )
I am a writer from Serbia, sorry for my bad English!

Let me try to unpack your logline:

Event: Earth's government begins a planet-wide genocide. (Of whom? Who are they targeting? Lower socio-economic classes?)
Protagonist: An astronaut on shore-leave.
Goal: Stop the genocide. (What is the thing your protagonist will have to do that will signify to the audience he/she has triumphed or failed?)
Stakes: millions of people. (How is the lover tied into this genocidal plot? Why is she in danger?)
Antagonist: Unknown. (There is no face to the villains).

At first glance, your logline is very muddled, but I think SOME of the elements are there, and some need refinement. Let me try:

"When the wife of an impoverished ex-space-cop is sent to a death camp along with thousands of other "undesirables", he and a rag-tag group of freedom fighters infiltrate government headquarters to overthrow Earth's powerful new fascist dictator."

Obviously, I've just inserted a pretty generic objective goal, but you need to provide clarity in your revised logline of what the goal will actually be, along with a clear causal link between your protagonist, his goal, and the stakes.