A young man that is unhappy from his desk job being a pushover and not taking seriously comes home frustrated to the point he decides to kill his young neighbor, however she gets free due to his ignorance of killing someone.

"Tired of being a door mat, a neighborly milquetoast kidnaps a young girl and tortures her in his basement but his plans go awry she begins fighting back."

"Tired of being a doormat, a neighborly milquetoast kidnaps a young girl and tortures her in his basement but his plans go awry when her determined boyfriend begins sniffing around."

Loglines are tricky, you want to tell people the main conflict but not how the conflict ends.

So in your story you have to ask, what is standing in his way and then put that in the logline?

I see, so how does " A young milquetoast unhappy with his life decides to a life of a friendly neighbor."

Might be my mistake, when you say in the logline she gets free, that sounds like the end of the movie.