You can unlock a special armor by collecting all the fragments of Ishtar's bones. With this armor you are immune to all damage making this play-through quite simple. However, there are three parts you will not have the armor therefore some skill will be needed. These are chapters 6 during the driving section, chapter 8 & chapter 9. You will have to fight some fallen angels & dark Enoch during these chapters. At first it might seem daunting but by learning their patterns & knowing when to attack you will have no problem defeating them.
Enemies can still break your guard and end your combos while wearing this armor. Also, the highest possible ranking you can get is S. So getting the conqueror achievement with this armor is out of the question. (thx to A Man in Flames for pointing this out)
Here is a link to a great guide by linkin10362 which has the locations of the bones of Ishtar: http://www.xbox360achievements.org/forum/showthread.php?t=32...
Hope this helps, If you have any other tips or suggestions to the solution please feel free to add.