Something odd i noticed in my playthroughs that i have now incorporated into new ones is the ability to "wipe the slate" with the NCR and Legion even if you have commited atrocities against them. "How does this work" you may ask. Well the answer is that once you have visited Mr House in his Tower for the 1st time you will recieve a note from an NCR messenger telling you Ambassador Crocker wants to see you, likewise after "dealing" with Benny and exiting the Tops a Frumentarii will give you the mark of Caesar. As long as you dont have the maximum negative rep from the factions you can have all your crimes forgiven at any point during the game.
Example: When you complete Lonesome Road you get the chance to bomb the NCR and/or Legion creating new irradiated area to loot and earning a ton of bad rep with the corresponding faction. After this you can travel to Vegas and speak to Crocker (only works the 1st time when he asks you to help with the "Boomer" situation) to have your crimes against NCR wiped. Now when you leave the Tops Casino or the 1st time and the Frumentarii gives you the mark, this counts as the same thing so you have to be sure not to deal with Benny until you need the forgiveness.
Now you are likely asking "if i wronged that faction then surely it was intentional and i dont want their forgiveness". Well i will give you an example of a characte ri made that required this system to fulfill it's purpose. I made an NCR affiliated character who i wanted to have Power Armor. Well that is fine BUT i wanted NCR power Armor and the only way to obtain legit NCR PA is to bomb the Long 15 Highway and take the Scorched Sierra PA from the mini-boss there. well as an NCR character i didnt want them to hate me so i did the Divide QL and then asked for forgiveness...now all is well and the character is befitting of his purpose.
Now the real point of this thread is to ponder...Why is forgiveness so easy to earn when you have caused such horrendous damage to the factions? As far as i am aware you could go as far as killing Chief Hanlon or Vulpes Inculta in full view of the Rangers/Legionnaries and then get forgiven anyways. This does seem an absurd notion (although in Caesar's case i think he is more willing to trade lives for useful assets) and i wondered what the communities thoughts were...