From the sheer volume of diagrammed play information, blocking assignments, options, etc that an NFL qb is expected to master in order to be effective in his role, I’d say that takes the cake for taxing; however, for stress in the moment, I can’t think of anything worse than the pressure of a match deciding penalty/free kick in World Cup soccer, or being the goalie in that moment, as the eyes of basically the entire world watch and a whole nation will figuratively live or die on that outcome...with no redemption possible for at least 4 years ?