You could name a half-dozen scenes in Akira that you might think are better than Tetsuo's hospital escape, and you wouldn't be wrong. From the opening motorcycle chase to the final showdown in the abandoned stadium, Akira is a movie made-up of fantastic scenes. Another favorite of mine is the street-level shootout where a man is gunned down by the police in front of stalled traffic. That brief sequence has some of the best animation in the whole film.
I'm hard-pressed to think of a scene in any film that displays raw psychic power better than the short sequence in Akira, when Tetsuo escapes from the government hospital. To this point, he's been abducted by the military as part of a program to force human beings up the next rung on the evolutionary ladder. They've succeeded once, with a child named Akira, who went so far off the scale that he became a being of pure energy. They're hoping to get Tetsuo almost to Akira's level, but still in some sort of form that they can control. Testuso's a street thug, a juvie who won't be missed by anybody, and the whiniest runt in a gang of teenage bikers, who don't take him seriously at all.
Maybe they'll take him seriously once they know that he has the ability to blow people up with his mind? After a psychic nightmare delivered to Testuo from the minds of the other children in the program (all of them, failed attempts), Tetsuo decides he's had enough of the hospital and leaves his room. When a doctor, flanked by two security guards, scolds Tetsuo to return to his room, the veins on Tetsuo's head twitch and all three men explode in a burst of gore.
Soon, the riot guards are on the scene. Tetsuo blocks a cannister of tear gas with his mind, creating a cool moment of animation as the smoke billows around Tetsuo's invisible psychic dome. Tetsuo pushes the dome out with a cry, tearing apart the walls, floor, and ceiling with his newfound mental powers as the shield expands. The hallway begins to crumble and several of the riot guards are pushed back by the force with an odd zero-gravity effect. Cut to a door at the end of the hall, that slowly opens as red smoke cascades around Tetsuo. The camera pulls back into the hallway, and we see that all of the riot guards are now dead, crushed by psychic force.
If you haven't seen Akira, I haven't spoiled a thing. The animation brings it to life in a way that my words just can't describe. It remains just a single scene I love (not even a pivotal one, really) in a movie that I love.