"[They] are terror-stricken at the growing workers' revolutionary movement.…Even though [they] are still raging, even though they may kill thousands more workers, victory will be ours." Which revolutionary leader would be most likely to have said this?

They made a checks and balance system to equal power within the branches. the "check" meant that one branch would watch one branch and "balance" them if they were too powerful. if you want more info on this, i would just google checks and balance system.