Since this has been bumped anyway, you can replicate what this plugin did with these settings:
Code:
tf_weapon_criticals 0
tf_weapon_criticals_melee 2
For the second cvar:
Code:
Controls random crits for melee weapons. 0 - Melee weapons do not randomly crit. 1 - Melee weapons can randomly crit only if tf_weapon_criticals is also enabled. 2 - Melee weapons can always randomly crit regardless of the tf_weapon_criticals setting.