izneveriti

1. (+ acc.) to let down; to fail
   Nikad te neću izneveriti. — I'll never let you down.
   Reprezentacija je opet izneverila navijače. — The national team let the fans down again.
2. (of trust, expectations) to betray; to fall short of
   Izneverio je poverenje svojih prijatelja. — He betrayed his friends' trust.
   Film je izneverio moja očekivanja. — The film fell short of my expectations.
3. (of memory, strength, body) to fail
   Pamćenje me je izneverilo. — My memory failed me.
   Na kraju trke noge su ga izneverile. — At the end of the race his legs gave out.

Takes a direct object in the accusative: izneveriti nekoga, izneveriti očekivanja. For marital infidelity the usual verb is prevariti (ženu, muža); izneveriti ženu is understood more broadly as 'to betray, to let down'.