Frank Vatrano scored a power-play goal, and Lukas Dostal made 37 saves for the Ducks (9-21-3), who had won two straight and were seeking their first three-game winning streak of the season.
"We had a good thing going there, a couple wins in a row coming into a rivalry game," Anaheim defenseman Cam Fowler said. "We would have liked to have a better showing than that tonight, but give them credit. They did a good job capitalizing on their opportunities, and that was the difference in the game."
Doughty put Los Angeles ahead 1-0 at 6:46 of the second period on a slap shot from the high slot set up by Anze Kopitar.
Vatrano tied it 1-1 at 14:27, getting position in front of the net and putting in Kevin Shattenkirk's rebound on the man-advantage after the Ducks had committed three straight penalties.
"We're not a team that scores a whole lot, and having the other team have an extra guy on the ice is not a good plan," Anaheim coach Dallas Eakins said.
Iafallo gave the Kings a 2-1 lead at 19:39, getting the tap-in at the left post off a pass from Phillip Danault.
"It was good that everybody bought in," Iafallo said. "Everybody's kind of making small plays, talking out there, talking in the locker room. We got to keep doing that going into Christmas break."