This is a solution for the final boss fight against a certain General. I know that this is not a solution for the entire game on the Über-Difficulty but I want to post this here to save you all some time if you are struggling.
At first you have to shoot down the two Zeppelins that are flying in the air at two corners outside the fighting-area. When the fight begins quickly go behind the glass-wall and cut a hole in the fence with your laser gun. You'll find your weapons there and some health. Collect all health and armor when you are running around - you'll need it!
You need to get up to the Flaks to shoot down those Zeppelins. To get there try to shoot the General a few times with your lasergun - he then will recharge his shield - this is your chance to run to one of those Flaks. Shoot down the first Zeppelin and repeat the process to get to the other Flak.
Phase 2 is the one that can be the most frustrating but there is one way to make things easier: Double-Rockets!!
Before you get down the hole be sure to collect your weapons and all ammo you can find. Equip both Assault Rifles and switch both to rocket mode (press right on the D-Pad, then Press left on the D-Pad). Be sure that both Rifles are equipeed with rocket ammo and jump down the hole.
As noted by "Craig Buchan" you should also open the wooden boxes to collect some extra health!
The moment you jump down you will see some rocket ammo in front of you - take it. There is another little stash of rocket ammo in the far left corner (up the stairs and then in the far left). Give yourself a few runs to locate those to make your fight easier.
From then on it's all about hitting him always with two rockets at once, then run around a few seconds - then again double rockets (spamming him cosntantly at once with your rockets will not do the Job!!! Shoot - hide a little bit/run away - shoot).
Repeat the process.
I think I needed 8 or 9 good double hits and a few single hits to bring him down.
Try to move around and watch out for the fire - it's hurting badly on that difficulty. There is some health and some armor lying around - take it only when you need it.There is also a simple way that worked for me: After collecting the rocket ammo run to the stairs and over the walkway in front of you- when you reach the other end of the walkway turn right and hide in the gap between the walkway and the wall. When you are hiding there in a good position the boss will not be able to hit you. You can then fire at his feet until he goes down. Give it a try - I can confirm that this works - did it on another Über-Run.
(credits for this way go to NeXuS23 who wrote this in his solution for the 360 Version!)
I hope I can save you some time with this guide. Good luck!
If you vote negatively please tell my why. Thx!PS: I replayed only the last chapter to get both achievements for Über and I am Death Incarnate Difficulties. As reported by other Gamers this is still working!
Dr.Schmock posted this videoin the comments showing that the stairs also work on the opposite side:
Here is another way with a Video guide from ZasterModa123: