The Collaborative International Dictionary of English v.0.48:

Needless \Nee"dless\, a.
   1. Having no need. [Obs.]
      [1913 Webster]

            Weeping into the needless stream.     --Shak.
      [1913 Webster]

   2. Not wanted; unnecessary; not requisite; as, needless
      labor; needless expenses.
      [1913 Webster]

   3. Without sufficient cause; groundless; causeless. "Needless
      jealousy." --Shak.
      [1913 Webster] -- Need"less*ly, adv. --
      Need"less*ness, n.
      [1913 Webster]

WordNet (r) 3.0 (2006):

needlessly
    adv 1: without need; "it would needlessly bring badness into the
           world"

Moby Thesaurus II by Grady Ward, 1.0:

19 Moby Thesaurus words for "needlessly":
   aimlessly, beyond need, beyond reason, bootlessly, fecklessly,
   fruitlessly, futilely, overplus, pointlessly, purposelessly,
   redundantly, supererogatorily, superfluously, tautologously,
   to little purpose, to no purpose, unnecessarily, uselessly,
   vainly