how do points gathering work with arch enemies? i.e., do i have to use sentinel to kill an xman or brotherhood to get double points or does ANYBODY on my team kill an xman or brotherhood and i still get double points because i had their archenemy? or does the archenemy have to deliver the killing blow?

You have to acutally KO the fig with the arch enemy. Mr. Fantastic has to deliver the killing blow to Doc. Doom, any of the other FF KO'ing Doom only score regular points. I actually did ko doom with fantastic last night I couldnt beleive it they are so lopsided.

ok how about this. someone s standing on the other side of the wall and i shoot down the wall, does the rubble damage the person standing on the other side? thanks!

No, but if you have flurry you can break the wall with the first attack - provided you do the required damage - and then use the second attack to hit the person on the other side.