Where do you get that a naked human vs a titan is a -2?
I would apply an incredibly larger than that penalty for those circumstances.
There is no rule saying that any penalty must be only -2 and no more so speaketh the lords.
Intimidate works just fine if the GM applies reasonable adjustments for circumstances.
it also works fine if the GM reads the skill and sees that it allows you to change the behavior, not control the behanior, not dictate the behavior.
you can intimidate someone into stopping what they were doing, but you do not determine, control, dictate what their new behavior is.