Wiktionary
pessimistically
adv. In a pessimistic manner.
WordNet
pessimistically
adv. with pessimism; in a pessimistic manner; "he evaluated his chances for survival rather pessimistically" [ant: optimistically]
Usage examples of "pessimistically".
But the rate of his progress was such that he pessimistically calculated that it would take him at least two years before he could preach with any degree of understanding in the Athabascan tongue.