Brother Eye and his OMAC virus would be a crucial treat.
Once the the heroes realize humans are trapped inside, they'll hesitate.
Superman and his Legion of robots backed with New Gods tech, Brother Eye, Amazo adaptoid abilities would make them pretty beastly.
I could just summon the Legions and there foes to help.
I would have Manchester black and Maxwell Lord with enough time mind
control the likes of Thor and few other Heroes and Villains and let them go wild on the Earth.
Zoom, Inertia, Professor Zoom, Barry Allen, Wally West, Johnny Quick and Bart merged with the Speed Force just start killing left and right.
If i don't want to do all that planning, i could just have Superman use the Miracle Machine.