quickliest

Adverb

1. superlative form of quickly: most quickly
   • Yet, in the very centre of the crowd, To keep the secret of a poignant scorn, Howe'er to airy Demons suitable, Of all unsocial courses, is least fit For the gross spirit of mankind, — the one That soonest fails to...
   • Go, go, pass within, as you quickliest can. - 1868, Augusta Webster (transl.), The Medea of Euripides, page 13, line 105