Some of the reports say they pulled 10Gs during their landing.
The nice thing about Soyuz is that it's a very forgiving design. A normal re-entry should use the capsule's shape to develop some lift and reduce the load on the passengers, but if something goes wrong, the ballistic trajectory ensures that they get home in one piece.
The modern Soyuz is a relative of the Soviet Soyuz 7K-L1 probes (with the spooky name Zond) sent around the Moon between 1968 and 1970. These were designed to become the first manned missions to pass behind the Moon beating Apollo 8. At the time the Soviets knew they couldn't beat America to the landing, but they could get some publicity for the missions and test their lunar hardware. However,problems with the capsules and the Proton booster caused the manned program to be cancelled.
One of the problems with Zond was that it had a nasty tendency to make ballistic re-entries in excess of 20Gs.
That'd be nasty.
Zond returned some stunning, and rarely seen, images of the Earth and the Moon, you can see a few of them at: