Bryan Habana scored his 40th Test try, with all of the defending champions’ points coming in the first half.
And despite a mighty effort, and George Stowers’ try, Samoa — who were reduced to 14 men when Paul Williams was sent off late on for punching Heinrich Brussow — were unable to keep their last-eight hopes alive.
De Villiers said: “It’s very good for us. We’ll never find a more physical game in this tournament. I think we played complete rugby. In the first half we attacked with everything we could and in the second half our defence never let us down. We’re ready for the next phase.”
The Springboks are poised to play the Pool C runners-up — most likely Tri Nations champions Australia — in the quarter-finals in Wellington next Sunday as they bid to become the first side to retain the World Cup.
De Villiers added: “We never came here to defend anything. We came here to compete. The team that won the World Cup four years ago might have a lot of the same names. It’s not the same team. For us to come here only to defend would be to sit on something. We want to work hard to become the champions again.
“Everybody called this the pool of death. We knew this was going to be tough. The guys that we played against are quite high up in the rankings. Now it’s all systems go.”
South Africa also finished the match with 14 men after captain John Smit, on as a replacement, was shown a yellow card for kicking the ball away following a deliberate knock-on.
De Villiers was angry with referee Nigel Owens’ punishment.
He said: “It was a stupid decision to get him off the field. I don’t think he deserved a yellow card.”
Samoa’s failure to get a losing bonus point means they are set to finish third in the pool and Wales should advance as runners-up, barring a major shock against Fiji on Sunday.
Samoa captain Mahonri Schwalger was frustrated and disappointed, saying: “We gave it all we got. I think the ref was pretty hard on us.
“The sending-off — a little bit of acting out there.
“There was nothing in that, but the referee gave him a red card.”
Third place in the pool will secure qualification for the 2015 World Cup in England.
Samoa head coach Titimaea Tafua dismissed the notion failing to advance to the knockout stages meant it was a poor tournament for his side. Tafua declared: “Everything is okay.”
SOUTH AFRICA: Lambie, Pietersen, Fourie, F. Steyn, Habana, M. Steyn, du Preez, Mtawarira, B. du Plessis, J. du Plessis, Rossouw, Matfield, Brussow, Burger, Spies.
Replacements: Hougaard for Habana (47), Steenkamp for Mtawarira (62), Smit for B. du Plessis (69), Alberts for Spies (61).
SAMOA: Williams, Lemi, Mapusua, Fuimaono-Sapolu, Tuilagi, T. Pisi, Fotuali’i, Taulafo, Schwalger, Johnston, Leo, Thompson, Tuifua, Fa’asavalu, Stowers.
Replacements: Mulipola for Taulafo (77), Avei for Schwalger (77), Perenise for Johnston (60), Tekori for Leo (60), Treviranus for Tuifua (73).
Referee: Nigel Owens (Wales).