Unaugmented mundane nightmare., Creating a viable villain without 'ware or magic. Options

[FuelDrop]

Here's the plan: an antagonist for a group of runners who, without 'ware, magic or technomancy, is dangerous enough to make the group reach for their guns at the mere mention of their name.

Now my initial plan was to go the 'Joker' route: Insane, enjoys collateral damage, lots of explosives and poisons, lots of expendable gang muscle who're too fanatic/crazy to run away even when hopelessly outmatched. He wouldn't be a match for the group's combat characters in a straight up fight, but that's what minions are for, right?

Then I thought of the 'Lex Luthor' route: Powerful businessman masterminding a series of black ops that the team manages to get in the way of. someone untouchable, or near enough, who they have to defuse somehow.

Any suggestions of more types of mundanes that can be really scary to shadowrunners, and how to run them?