Source : Webster's Revised Unabridged Dictionary (1913)

Leniently \Le"ni*ent*ly\, adv.
   In a lenient manner.

Source : WordNet®

leniently
     adv : in a permissively lenient manner; "he felt incensed that
           Tarrant should have been treated so leniently given his
           crime" [syn: {laxly}]