I think it would be LexCorp, LuthorCorp is only used by Smallville to differentiate between Lionel and Lex's separate enterprises.

"Let us remember that there is a creative force in this universe, working to pull down the gigantic mountains of evil, a power that is able to make a way out of no way and trasform dark yesterdays into bright tomorrows. Let us realize the arc of the moral universe is long, but it bends toward justice."
-- Martin Luther King Jr.