HackerVoca

unassuming : modest, unpretending, unpretentious, humble
unbearable : unendurable, intolerable, insufferable, insupportable
unbecoming : inappropriate, unsuitable
unbiased : fair, impartial, unprejudiced, disinterested
unbounded : unlimited, boundless, limitless, immense,
immeasurable, vast, infinite, endless, interminable / adjective
very long and boring: interminable delays
interminably adverb : an interminably long speech

uncivil : impolite, discourteous, impudent
uncompromising : unyielding, inflexible, rigid, firm, obstinate
undergo : experience, suffer
undermine : ruin, thwart
undertake : assume
unequaled : unparalleled, matchless, peerless /adjective
better than any other: Torvill and Dean's peerless performances in ice dancing

unexampled : unprecedented, matchless, peerless