Alex is the human persona taken on by Skynet. Skynet, the core and master of the machines, is the technically the main villain of Genisys, therefore, possibly the entire Terminator franchise. It claims that it's not a machine, therefore, unlike the Terminators, it's not a slave.In Genisys, when Kyle Reese is in the process of being sent to 1984, Alex sneaks up on John Connor and attacks him. Revealing himself to actually being Skynet he asks John, You didn't think this was gonna be easy? then he proceeds to kill the remaining Resistance soldiers in the hanger before turning John into the T-3000.