If your like me, and you didnt get all the "kill X amount using specific gun" trophies, here are a few tips that might be helpful
First, try to do the gun specific trophies and challenges as soon as you get that power.
Leave all the target activities for gun kills, because that just makes it easier
If you did do all the target activities, hopefully you didnt unlock the kill bots (which come in fairly quickly if your leaving this for the last clean up)
Now again this might help if you did everything and are missing stuff
1) Go into a building. Most of the weak zin either run in or super run in, both of which is fine as its a confined space, and by now health shouldnt be a problem. ALso, lets say the portals are popping out kill bots. In a building the heat on you can decay, leaving more zin and less machines or flying guys.
2) Run away and wait till a portal opens up near you. If its zin, you can kill 2 towards what ever challenge or trophy your doing. Note that this works for both powers and guns. If that portal gives you kill bots, wait for another to arrive. This next portal is gaurenteed zin.
3) Combo your skills. Things like stomp are hard to do because most zin jump away. Freeze them, and then hopefully it counts as a stomp kill as well as a shatter
Last thing that isnt really a tip but a question.
I beat the game in 20 hours. Has anyone else had to grind out the time like i have? I am actually leaving it on all night tonight, just to get the last 8 hours i need. I did this for saint row 3 also, but now its 40 hours. I think the last time it was only 3o.
I also am sitting here with 14 hours of time to kill, I think I'll play another game and leave it on all night and through work tomorrow. Some tips I have for getting X amount of kills; I had beaten the game and done everything, just had to get X amount of kills for several things and was having trouble doing so because most of the aliens that show up after you beat the game are them big robots and flying vehicles. So what I did was play the fight club missions over again because I had remembered about the waves where you play king of the hill, there is an endless supply of aliens to fight. Don't defend the area and you will have aliens after you in groups of 5 - 10. However, they don't count if you reach the time limit and fail, you have physically exit out before the time is up. Then don't hit retry, exit the mini game, then go back in from there. In just two rounds I was able to knock off 4 different challenges.
for the trophy I Am Become Death (Kill 1000 Aliens With Any Combination of Super Powers), you don't need to use 2 or more super powers to kill 1 enemy. I'm at around 940 out of the 1000 and I've only got maybe 25 or so that I used two different powers to kill. The biggest one I used, which got me about 600, was the freeze blast. I froze em and shotgunned them for a shatter kill and it counted. while working on the stomp trophy/challenge, all i did was go up to a cluster of enemies and press R2. granted i had to do that multiple times to get most of those kills with stomp, but nonetheless i only used the 1 power.