unsparingness

from The Collaborative International Dictionary of English v.0.48

Unsparing \Un*spar"ing\, a. [Pref. un- not + sparing, p. pr. of
   spare.]
   [1913 Webster]
   1. Not sparing; not parsimonious; liberal; profuse. --Burke.
      [1913 Webster]

   2. Not merciful or forgiving. [R.] --Milton.
      [1913 Webster] -- {Un*spar"ing*ly}, adv. --
      {Un*spar"ing*ness}, n.
      [1913 Webster]