I've been doing aikido for about 9 months now, and I'll tell you, it's not an art you can "whoop ass" in in a short time frame. I was a varsity wrestler, and I can tell you that I'd immediately fall back on wrestling (my coach also taught us WHY some moves were illegal... namely, the joint-breaking aspects of them) before aikido. However, I really enjoy aikido, and it's incredibly effective at the upper levels. With just a few small half-turns, you can obliterate someone else's balance and break their neck, wrists, elbows, etc.
But, I tell you, if you study aikido to beat ass, you'll quit it shortly. Aikido is one of those arts you practice because you enjoy it. If you just want to be a bad-ass, try jiu-jitsu, a hard-style karate, or boxing, as you can become at least slightly proficient in them in a (comparatively to aikido) short time.