However, with properly-adjusted dual-pivot brakes (these brakes came on a lot of the bikes that had suicide levers) it's quite easy to generate lots of braking force.
The brakes that came on many of the cheap, low line bikes with suicide levers were more commonly called centerpulls. They were "dual pivot" in that each arm was mounted on it's own pivot but currently the term is applied to a specific design of sidepull brakes.
The bikes I bought for my kids in the late '70's had centerpull brakes that were dreadful because the arms were so flexible they couldn't generate any real force and the "suicide levers" exacerbated an already bad situation.
Good centerpull brakes work well but there weren't many good ones out there.