danggg this in challege mode is insanely hard. Without the RYNO your basically scrued.
just spamm your high impact weaponry, i only had trouble with the Thug 4 Less robot that held Angela…
I didnt recognize anything harder than before, maybe because i was too concentrated to kill enemies… 
it is very hard it take about five mini rocket tube shots to kill any anemy and the ankle biters take like 3 wrench hits.
well i think its because the mini rocket tube is not such a good weapon..
ya ik but ita one of the 7 i relyed on in regular mode now its uselesss.
Use the Heavy Bouncer & Heavy Lancer (fully upgraded). This game is good for being the game with all the insane firepower! Because of these key weapons (Heavy Lancer, Heavy Bouncer & Tesla Barier) i am able to go through challenge modes with just my first armour! Try it, i dare ya to 
Personally the only reason I died alot in challenge mode was because I wanted to upgrade everything, like the weak mega weapons. Otherwise, I don't find it really that hard.
Challenge mode isn't hard except when like stated b4 when you try upgradin weak weps and then all ur guns are like 1 or 2 lvls behind what theyre supposed to be >.< and yea rocket tube stunk in challenge