Ronaldo was at a FIFA briefing with ex-Germany captain Lothar Matthaeus and former Italy skipper Fabio Cannavaro and, while there was good-natured sparring ahead of Tuesday's semi-final between Brazil and Germany, he condemned defender Zuniga's foul.
"It was a very violent, unlawful tackle," said Ronaldo.
"We all have to fight for football to have more fair play. We have to demand that sanctions be given to violent players. I am in favour of very severe sanctions to those who don't want to play football and just want to do such violent tackles.
"It was an evil tackle," he added.
Zuniga damaged Neymar's third vertebra when he came rushing in from behind and kneed the Brazil forward in the back.
In a letter to Neymar and Brazilians on Saturday, Zuniga wished him a speedy recovery and insisted there was no ill will.
"I feel upset for this situation which came from a normal action in play, without ill intention, malice or imprudence on my part," he wrote.
Sympathisers, who note Zuniga was looking at the ball and not Neymar when he went into the challenge, say it was an unfortunate accident in a rough game with lax refereeing.
"I want to send you a special greeting, Neymar. I admire and respect you, and consider you one of the best players in the world," Zuniga added.
"I hope you recover and are back soon to keep cheering us up in a sport full of virtues and qualities that I've always practised in my 12 years as a professional."
Brazil's Ronaldo added that while the quality of refereeing at the World Cup had been generally good, the performance of Spaniard Carlos Velasco Carballo during Friday's quarter-final against Colombia, which Brazil won 2-1, did not impress him.
Carballo, a top UEFA Champions League referee, did not book anyone until there had been 41 fouls and, although Neymar was left in agony on the ground and quickly carried off on a stretcher, Zuniga was not booked for the incident.
"The referee lost his authority on the pitch," said Ronaldo although he disagreed with the comments by Brazil coach Luis Felipe Scolari, who said after the game that he thought the Colombians were "hunting" for Neymar.
"I don't believe there was a 'hunt' for Neymar, but we could see there was an intention by the Colombia player to harm him," Ronaldo said.
Ronaldo knows all about pain at a World Cup.
Although he scored the two goals that gave Brazil a 2-0 win over Germany in the 2002 final, he suffered with illness or some other ailment in 1998 and performed well below his best in that year's final when France beat Brazil 3-0 in Paris.
Ronaldo said he felt great sympathy for Neymar and, after learning of the severity of his injury, contacted him in hospital.
"I sent Neymar a message, conveying my support and solidarity. I told him the whole country is proud of him and the team will win the World Cup and dedicate it to him," he said.
"I felt the physical pain of the strike he suffered and the worst pain of having to abandon the World Cup. This is the World Cup in Brazil. Neymar had so many dreams, playing a World Cup in his own country, in front of his people.
"He's suffering a strike from life, having to abandon this World Cup."
Matthaeus, who led West Germany to success in the 1990 World Cup, said: "Neymar's injury came as a shock to us.
"Some people will think we have an advantage (in the semi-final) but we want to play against the best of the best. Neymar is one of those players who can make the difference.
"We have tears in our eyes when we see the image of Neymar yesterday and heard the information about his injury.
"All German fans wish him a speedy recovery."
Cannavaro, Italy captain when they won the World Cup in 2006, said: "I believe it was a situation that could have been avoided.
"I didn't like that high knee. It was a foul with intention to cause harm. It will be very hard for FIFA to accept because it is a very evident foul."
FIFA spokeswoman Delia Fischer said soccer's world governing body would evaluate the match, as it always does, after receiving the referee's report. Barcelona forward Neymar is likely to be out of action for six to eight weeks.