When a cop determines that the ends justifies the means in keeping the streets safe he falls from grace and finds himself on the wrong side of the law running for his life.

Get specific. Fall from grace, wrong side of the law, these are too vague, too overplayed, for anyone to either want to invest in or see your movie. I know your movie is about a cop ... and something happens, and someone is after him, by the sounds of things, to kill him. But I need specifics if I'm to remember this film, or be more interested in this film, than a dozen other similar sounding films.

I agree- the inciting incident, the goal, the antagonist and the stakes. Essential ingredients. If it is high concept enough to grab us you don't need to describe the inner journey with reference to flaws in the hero and bad guy.

"Ends justifying the means" is a common ethical dilemma that is frequently explored in cop flicks and shows. What's the hook -- what is unique, different, original in this logline?

The logline speaks in generalities when it would benefit by being specific. What, exactly, is the inciting incident that precipitates the "fall from grace". Who is the nemesis? (And I use the word 'nemesis' in it's classical sense: it's more than just the antagonist, its the agent of dramatic revenge for violations of the moral order. Which is certainly the case in this premise.)