Here's a tip for final battle in Gunslinger Joe part 3 that can help you to get mein leben achivement:
When you are fighting Citade (big robot that shoots rockets), you can actually shoot off his "rocket hand". This takes 4-6 rocket fired at his left hand, after that he will loose it and he is just standing there in the center of the map (! do not run close to him!). So at this point of game, when there are not soldiers running close at you, you can recharge (cool down) your suit without Citadel fireing at you and then finis him with the gun from heavy or any other gun (you should have enough rockets left so it is up to you).


Few more tips for part 3:

- Best way for me to go through part 3 was to fire in each part where there were commanders. They are usually separated from previous part of map by doors, so you can raise alarm and then run back to safer position, shoot everybody running at you and then commander will run at you too

- at beginning of final battle, I went with shotguns up to left (picking up healths and armor) and quickly killed soldiers (3-4?) and 2 commanders there before start firing at Citadel

- do not stop moving around until Citadels left arm is disabled

- Try boss fight at IADI first to be sure you know what you are doing.

- This should also help you with the Venusian Expert achivement.