The trick I've found with the Bulletwitch difficulty levels is that your gameplay changes. On the first 3 difficulties, this game is more a 'Go out and get'um' attitude.
But for the newer gamers out there that might find the last two difficulties (Chaos & Hell modes) too much for them, the trick is to change your gameplay.
Using stealth, hiding & strategy is the key here. On some of the maps, you'll find yourself hiding for quite a few minutes around a corner or behind a car for example. This gives the baddies a certain amount of time to 'cycle' and change up depending on how the map was written, along with the character movements, etc.
Using patience, and stealthy killing methods are key to getting through Chaos mode versus the 'kill everything in site' method towards the rest of the game.
On another note: If you are a completionist, and/or just HAVE to see that infamous HELL Mode 1 (one!) gamerpoint on your card, then know this. The final difficulty level is actually programmed a bit easier than the prior HELL Mode. It will take you a number of hours on this difficulty alone, but, if you're like me, you just couldn't stand the thought of being in the world-famous "Bulletwitch 999' crowd.
Getting the full 1000 is definitely street cred with other gamers. The devs knew this, and IMO this was quite funny to do to us.
So play slow, stealthy and especially use your map-memorization to get through these last two difficulties. Strategy and sneakier movements in these later levels is, IMHO, where this game actually shines.
PS - If you want to really have some hot, HOT eye candy during your play, download the free 'Secretary' outfit for Alicia. This is what actually made the game more interesting for me I swear. It made my hours on this title MUCH more bearable.
This outfit is amazingly hot to watch. (You'll see). Aside from (playing as) Amanda in Lara Craft: Tomb Raider Legend, Alicia with the secretary outfit is the hottest videogame chick so far. If I had Alicia & Amanda (in real life that is), I would just about die from happiness & protein loss and never leave the house.