What do you mean by Powerful?
What are you trying to do?
Some are more powerful than others for Animation, but I can't think of anyplace else where the term "powerful" applies consistently to many programs.
I have 3 favorite Fractal Generators to suggest.
Chaos Pro (
http://www.chaospro.de), Chaoscope (
http://www.chaoscope.org), and the Latest Addition - Mutatorkammer (
http://www.fractalmovies.com)! (Mutatorkammer is made by a member here!) Endlos looks Great, and is made by a member here too, but I have troubles with it's Java stuff. My computer has issues and needs to have it's operating system re-installed... But I digress...
Check the Image Thread for examples of stuffs I made with each (and sometimes more than one!) (Mutatorkammer can work with images, so I plugged in some Fractal Images made with Chaoscope and got some wonderful results!).
Have Fun!