Without wasting time, Viloria attacked Soto right after the opening bell and immediately scored two successive knockdowns from a series of right hooks.
For a while, Soto was able to recover from the twin knockdowns, but Viloria used his left hand to finish Soto with power shots to the body and head.
Referee Zachary Young did not bother to do the count as he stopped the fight at 2:02 of the first round.
It was Viloria’s fourth straight win since losing to Juan Francisco Estrada by split decision at the Venetian Resort & Casino in Macau, China, in 2013. That was a painful defeat for Viloria because he lost his WBO and WBA flyweight titles.
Viloria had a very impressive comeback victories after the loss to Estrada, starting off with a unanimous decision win against Juan Herrera in March 2014 followed by successive knockout wins against Jose Alfredo Zuniga and Armando Vasquez.
The impressive wins could set Viloria up for another world title fight. One of the possible opponents for the Filipino-American is unbeaten WBC flyweight title holder Roman “Chocolatito” Gonzales of Nicaragua.
“I know I have what it takes to defeat a fighter like Gonzalez. He’s been dodging me the last couple of years,” Viloria said after the fight.
The other prospect is a rematch with Estrada, who has held onto his titles six times in a row for the past two years.
With his fourth comeback win, Viloria raised his career record to 36-4-0 with 21 KOs.