Synonyms for Dismaying:

n.

dismaying (noun)
appalling, alarming.

v.

alarming (verb)
alerting, shocking, frightening, signaling, Scaring, panicking, startling, alarming, surprising.
dejecting (verb)
Dissuading, Disinclining, daunting, dampening, Dejecting, Deterring, disheartening.

Other synonyms:

Other relevant words:
appalling, alarming.