In Iron Man, after Pepper Potts uncovers Obadiah Stane's previous attempt to have Tony Stark assassinated by the Ten Rings, Obadiah reacts by immediately going to Tony's house and stealing his Arc Reactor, leaving him to die. He then uses the Arc Reactor to power his own suit and goes on a rampage with it, attempting to kill Pepper Pots and several government agents who were coming to arrest him.
But what was his actual plan? It sounds like he's trying to cover up the evidence of his guilt, as he tells Tony "Too bad you had to involve Pepper in this, I would have prefered that she lived.", but his actions after that point are far from subtle. Mounting an armored power suit and killing several government agents who were already coming to arrest him seems like it would only create more evidence of his guilt, so what was he hoping to achieve by that?