Well I had to kill 6 or 7 troopers in Freeside, not really my choice it was kinda just thown at me. A Ranger pays me a polite visit and tells me I got three days to straighten things out or I'm dead.

I do three quests for the NCR: (scouting out Cotton Cove, clearing the ants off the highway and checking up on Nipton). It took my three days and my Reputation is still "shunned", the Rangers are gonna come after me when I leave town.

I need to to lower my Infamy with the NCR any tips? Or is it too late now?

**possible spoilers**
If you are using PC, it is possible to use the faction cheat . Otherwise, I suggest loading another savegame. If you don't wanna go back to another savegame I suggest helping out in Camp Forlorn Hope/HELIOS one and do all the quests. Also if you haven't reached TOPS casino yet i think if u go there, kill benny and go out, legion and NCR both should reset to neutral.

Thanks but I was already offered amnesty by NCR and the Legion, I'll check out those other places you suggested I can keep ahead of the Rangers by fast traveling. If not I can load up a save I did yesterday.