By Arasu Kannagi Basil (Reuters) -Fiserv's shares plummeted nearly 42% on Wednesday and were set for a record single-day drop after the payments software company reported results below estimates and cut its growth forecast for the second consecutive quarter, with analysts calling the earnings "shockingly bad". The disappointing earnings highlight growing pressure on the fintech's core payments and merchant business, which has struggled to maintain momentum amid fierce competition and a slowdown in consum ...