The Collaborative International Dictionary of English v.0.48:

Mishandle \Mis*han"dle\, v. t.
   To handle ill or wrongly; to maltreat.
   [1913 Webster]

WordNet (r) 3.0 (2006):

mishandle
    v 1: make a mess of, destroy or ruin; "I botched the dinner and
         we had to eat out"; "the pianist screwed up the difficult
         passage in the second movement" [syn: botch, bodge,
         bumble, fumble, botch up, muff, blow, flub,
         screw up, ball up, spoil, muck up, bungle,
         fluff, bollix, bollix up, bollocks, bollocks up,
         bobble, mishandle, louse up, foul up, mess up,
         fuck up]
    2: manage badly or incompetently; "The funds were mismanaged"
       [syn: mismanage, mishandle, misconduct]

Moby Thesaurus II by Grady Ward, 1.0:

67 Moby Thesaurus words for "mishandle":
   abuse, batter, be negligent, beat up, befoul, botch, bruise,
   brutalize, buffet, bugger up, bungle, convert, debase, defalcate,
   defile, desecrate, destroy, divert, do violence to, do wrong by,
   do wrong to, embezzle, foul, fuck up, harm, hurt, ill-treat,
   ill-use, injure, knock about, knock around, maladminister,
   maltreat, mangle, manhandle, maul, mess up, misadminister,
   misapply, misappropriate, misconduct, misdirect, misemploy,
   misgovern, misguide, mismanage, misrule, mistreat, misuse, molest,
   muddle, muff, outrage, peculate, pervert, pilfer, pollute, profane,
   prostitute, rough, rough up, roughhouse, ruin, savage, screw up,
   violate, wreck