How to block/disable WiFiKill effectiveness on WiFi network? I just gave WiFiKill app to someone I know in the region where the college is and I guided him how to get it work. That was before the ending of holiday. 

At these days after holiday ended, he monitored that college WiFi network cutting all bandwidth on other connected devices, although they're connected to network. I hear all of them complain about the Internet while he's enjoying full internet bandwidth, which is not fair at all because that internet is only dedicated for college students only, not for citizens of that region.

How to disable this app affecting college WiFi network? What will happen if 2 users using WiFiKill on the same network and each one of them block internet on the other device?
Pretty much.. no. WiFiKill uses ARP poisoning to cause computers on the local network segment to use the wrong MAC address for the router, resulting in all packets being dropped. A second device running WiFiKill would have no visible effect; however, if you could spoof ARP reply packets which have the correct MAC address in them it could be used to mitigate the effects -- maybe. The two devices would be in a race at that point.