According to Helsingin Sanomat (Helsinki News) using information of the Sauerland Team test machine, Robert Helenius has punching power better than e.g Mike Tyson ever had.
Personally i don't trust much these "tests". On the other hand can we be sure that Tyson really punched harder than best punchers of our time? Comparing almost any sports we know that old world records have been crushed by new generation stars. Why would professional boxing make exception?