The word antithetically is playable in Words With Friends™, no blanks required. Because it is longer than 7 letters, you would have to play off an existing word or do it in several moves.
Words With Friends™ Letter Score: 24
Highest Scoring Words With Friends™ Play In The Letters
Seven Letter Word Alert: (38 words)
aclinal, acylate, alethic, alicant, analyte, anthill, attache, cattail, cattily, chantey, chattel, chitlin, ciliate, cleanly, cyanate, cyanite, cyathia, etchant, ethical, helical, hellcat, hyaline, hyalite, ichnite, lacinia, lactate, lacteal, latency, lattice, lithely, nattily, nictate, tacitly, tactile, tenthly, tetanic, titanic, yachtie