If there was ever a company hiding their true evil nature it was Buckaroo Banazi's Yoyodyne Propulsion Systems. Seemingly a defense contractor, the company was actually just a front for exiled red Lectoid aliens from Planet 10. Their first act of evil was hypnotizing Orson Welles into convincing people his report of their invasion was just a hoax.
While not showing a lot of imagination in creating human identities (with names like John Bigboote, John Smallberries, John Yaya, etc.), Yoyodyne was able to convince the Pentagon to give them billions. Instead of building a promised new bomber, they were actually building a ship to return to Planet 10 and free their comrades trapped in the 8th dimension. They were also willing to kill any humans (or as they called us, "monkey boys") that tried to foil their evil plans.
And their conflict with the Black Lectoids almost led to sparking a global nuclear war, but luckily Buckaroo (who happens to look a lot like Robocop) was able to stop them.