Yoda is definitely not it.
We don't know who is more powerful, Gandalf the White (after rebirth and getting the Elvish ring) or Sauron with The One Ring Of Power on, or whether Gandalf would have been more powerful than Sauron if he ever put on the ring. Or maybe Galadriel with the ring would have been more powerful? We don't know, those are all theretical possibilities which never happened in their universes.
Albus Dumbledore is powerful, but he won't use his full abilities because of some moral code, so he won't stand a chance.
Tom Marvolo Riddle aka He Who Must Not Be Named aka You Know Who aka The Dark Lord aka SnakeFace aka Lord Voldemort 😉 is ok, but you can't really compare him with the most powerful wizard in Tolkien's realm because JRR and Joanne have a very different understanding of magic.
If Harry James Potter will curse Voldie's butt at the end of HP book7 (JKR is teasing saying he might die, but c'mon, he must win) he might be more powerful than Voldemort, so if comparing wizards at the peak of their power, it's either Sauron wearing the ring or Potter fully grown.
Tom Bombadil is a possibility too, but he is not a wizard.
Who is this Raistlin fellow you speak about? What book/movie?
The wizard of Oz? Bah.