It was just pointed out to me that Overwhelming Power only makes damage unpreventable, not attacks. I had not realized it was different from Overwhelming Force. I thought I would provide a handy table in case anyone else was confused.
Code:
Unpreventable Targeting Unpreventable Attacks Unpreventable Damage
Indiscriminate: X X
Overwhelming Force: X X
Overwhelming Power: X
Note that when Diplomat is in effect, you can neither target nor attack the character. You have to get around both restrictions. Indiscriminate does that. Overwhelming Force only gets around the attack restriction. But you can get around the targeting restriction by making a non-targeting attack (such as an attack of opportunity, Lightsaber Sweep, or Strafe).