pessimistic
Cassandra
Eeyore
calamity howler
crepehanger
cynic
damp
damper
defeatist
foreboding
fussbudget
gloomy
killjoy
malist
misanthrope
miserabilist
negativist
nihilist
prophet of doom
retreatist
seek-sorrow
spoilsport
wet blanket
worrywart
doubter
sceptic
skeptic
bear
pessimism
agnostic
fatalism
formalist
idealist
optimist
optimists
reactionist
skeptics