Could Dumbledore Beat Voldemort?

Albus Dumbledore's the most obvious person who can defeat Voldemort without even sweating (not that he has much sweat left, anyway). Rowling herself has explicitly stated in the books that Dumbledore is the only person Voldemort fears since he's actually no match against him squarely.

Is Dumbledore more powerful than Voldemort?

Dumbledore's power over Voldemort was primarily in his wisdom. ... Voldemort was always ready for anything, most often evil, because of his inhumanity and destructive power, as an individual and as a leader, which always made him weaker and less valuable than Dumbledore. Dumbledore had always shown great magical abilities.

How did Dumbledore not beat Voldemort?

Dumbledore wasn't trying to kill Voldemort. Dumbledore then sent a powerful spell at Voldemort, one which the Dark Lord was forced to block with a Silver shield; the spell did not harm the shield, but made a deep gong-like sound as it was deflected.