South Africa coach Rassie Erasmus said on Saturday that Argentina are a tough side to crack and "had to be softened up" before three late tries delivered a 48-7 Rugby Championship victory.
The Springboks needed one point to claim the title for the first time since 2019, but secured five to finish eight points above New Zealand. Argentina were third and Australia last.
South Africa dominated the scrums and line-outs as Argentina paid a heavy price for ill discipline with Pablo Matera red-carded and Mateo and Santiago Carreras both sin-binned.
"While we are trying to play a more attacking game, we still want to be physical, have scrum dominance, and our line-out worked very well tonight," Erasmus told reporters in Mbombela.
"Argentina tired trying to stop our tight five all the time – it was a bit like slow poison.
"It was a learning school for us last week," said the coach, referring to a 29-28 penultimate-round loss in Argentina.
"I did not expect that sort of scoreline tonight because Argentina are very difficult to play against.
"Things were really tight in the beginning and they kept us out. But we did not want to stand back, it was all about temperament and leadership for us.
"We have used 35 players in the Rugby Championship, but for the crunch games it is the older heads who pull us through.
"Argentina are physical, nippy and great on attack. Jerry Flannery (defence coach) was very nervous before the game, but we restricted them to just one try.
"We played brilliantly in stages, much better than we did last weekend. It was not perfect, but there was some really good stuff to build on."
Argentina coach Felipe Contepomi said: "The heartbreak is how we lost. We were never able to be the team we wanted to be tonight.
"When that happens it becomes very hard playing a team that has won the last two World Cup finals. They were better than us from the first minute to the last.
"I recognise that our players kept battling and working to get back into the match, but we did not do what we planned, especially when defending.
"It is disappointing, but part of learning – how to do better under pressure. You need to stay poised and believe in what you have done in training."