Does a face being smashed in with a fire extinguisher count???
A lot of good answers here, and I would put my two honorable mentions in the realm of just good old-fashioned great moviemaking, the way most posters did with mentions of Saving Private Ryan, Star Wars, and the like. Those are intense, unbelievably well-crafted and cinematic snapshots of brilliance.
No. 3 is Inglorious Basterds: ermagherd, the tension created in the scene where Cristoph Waltz’s German “Jew hunter” confronts the French farmer about the Jews he knows are being hid! You could cut it with a butter knife!
No. 2 is The Player: dudes and dudettes, if you haven’t seen this movie, run (don’t walk!) to your local video store and RENT IT! One of the most hilariously insightful films ever, and the long-take first scene is a masterpiece in every way.
However, if we mean powerful by something that really grabs us by the short and curlies and starts yanking away unmercifully?
Then I would have to say the first ten minutes of Irreversible was that kind of powerful. Good? Not too sure! Effective? You betcha!
I won’t spoil the ending: it’s a real schocker too, although not in the way you’d expect.
But boy oh boy, in these first ten minutes. The camera goes crazy, the sound design is wicked, and we’re spinning into a gay fetish club somewhere in the sleazy world of underground Paris. We know something intense is going on, but we have no idea what. The music is thumping techno, the lighting is hellish red and stuttering strobe light.
We pass by people in leather, spikes, and chains participating in group sex, bondage, fisting, and submission play. Until at long last, our hero gets to where he’s going, finds the man he’s looking for (perhaps!), and proceeds to smash his face in with a fire extinguisher. It is brutal. But wait, it gets worse: see the movie for more!
Gruesome stuff, and powerful too!