" fiendishly "

1: as in diabolically;

•  Synonyms : 

•  diabolically,

•  ill-naturedly,

•  inconsiderately,

•  insensitively,

•  thoughtlessly,

•  misanthropically,

•  disagreeably,

•  ill,

•  ungraciously,

•  unkindly,

•  balefully,

•  caddishly,

•  callously,

•  cruelly,

•  evil-mindedly,

•  felly,

•  hard-heartedly,

•  heartlessly,

•  inhumanely,

•  kindlessly,

•  mercilessly,

•  pitilessly,

•  ruthlessly,

•  soullessly,

•  unfeelingly,

•  bitterly,

•  enviously,

•  jealously,

•  resentfully,

•  acrimoniously,

•  antagonistically,

•  caustically,

•  envyingly,

•  hostilely,

•  invidiously,

•  obnoxiously,

•  rancorously,

•  venomously,

•  vindictively,

•  vituperatively,

•  contemptuously,

•  deprecatingly,

•  disdainfully,

•  scornfully,

•  bitchily,

•  cattily,

•  despitefully,

•  hatefully,

•  malevolently,

•  maliciously,

•  malignantly,

•  meanly,

•  nastily,

•  spitefully,

•  viciously,

•  villainously,

•  virulently,

•  wickedly

•  Antonyms : 

•  benevolently,

•  benignantly,

•  good-heartedly,

•  kindheartedly,

•  kindly,

•  affably,

•  agreeably,

•  amiably,

•  cordially,

•  genially,

•  good-humoredly,

•  good-naturedly,

•  graciously,

•  nicely,

•  pleasantly,

•  altruistically,

•  humanely,

•  considerately,

•  feelingly,

•  lovingly,

•  mercifully,

•  sensitively,

•  softheartedly,

•  solicitously,

•  soulfully,

•  thoughtfully,

•  compassionately,

•  sympathetically,

•  angelically,

•  divinely,

•  gently,

•  sweetly,

•  tenderly

1: of, relating to, or worthy of an evil spirit;

  * e.g., " ... a fiendish delight in playing cruel tricks "

•  Synonyms : 

•  cacodemonic,

•  demoniac,

•  demonian,

•  demonic,

•  devilish,

•  diabolical,

•  Luciferian,

•  satanic

•  Antonyms : 

•  angelic

2: having or showing the desire to inflict severe pain and suffering on others;

  * e.g., " ... shook with fiendish laughter as he watched his victims writhe in agony "

•  Synonyms : 

•  atrocious,

•  barbaric,

•  barbarous,

•  brutal,

•  brute,

•  butcherly,

•  cruel,

•  heartless,

•  inhuman,

•  inhumane,

•  sadistic,

•  savage,

•  truculent,

•  vicious,

•  wanton

•  Antonyms : 

•  benign,

•  benignant,

•  compassionate,

•  good-hearted,

•  humane,

•  kind,

•  kindhearted,

•  sympathetic,

•  tenderhearted