Acid Rock. It's so powerful that its powerful powerfulestness is beyond my power to listen to its powerfullying awesome powerfulingestness.

Heavy metal, except that once it reaches a certain point where it becomes too Speed or too Black, then it actually loses some of its power (being over the top).

There's no way I can group these because it depends on my mood and preference at the time. I like all of them though, plus I don't how to classify the different kinds of rock, there's too many genres. I mainly think classical, hip hop and rap, and music like metallica, trivium, in this moment, killswitch engage, atreyu etc is the most powerful sounding.

Classical hence why its mainly used in films to set the mood. Then Rock and metal.

Black metal
Heavy metal
Goth metal
Metal
Grunge
Rock n roll
Punk
Rap
Techno

What do you mean by powerful? The one's that make the most lasting impact on you are the most powerful. That can be any music, it doesn't have to jolt you out of your seat. Loud does not equal power.

Here's my pick just for fun.

Powerful:
Nirvana
Beatles
Bob Dylan
Frank Zappa
Leonard Cohen
Joni Mitchell
Joan Baez
Led Zepplin
The greats from the 60s Hendrix, Cream etc
The greats from the 70's Tom Petty Fleetwood Mac
The greats from the 80's Grunge
Pearl Jam and the Seatle Sound Industrial Rock like Korn
90's? Lots of crap

What do you mean by powerful? If you mean the biggest most awesome sound, I would vote for "progressive rock," which isn't on the list. Bands such as "Yes," and "Chicago," which have taken rock composition and arrangements to the max. If by "powerful" you mean "getting the message out to the people," I would vote for folk music, which has traditionaly always been a message set to music. Punk music also originated as a means of expressing feelings about topics of importance to youth.

Rap imo it goes into the issues of life and others hardship and in the end it makes me think there is always tomorrow. It gives the message as it is.