pessimist

If the world can be divided into those who see the glass half empty and those who see the glass half full, the half-empty crew are known as pessimists––they always see the worst.

The opposite of pessimist is optimist––someone who always sees thing in a positive light. Most people insist they are optimists, and when accused of pessimism suggest they're only focusing on reality. In fact, though, people who see reality as it is are called "realists."

Definitions of pessimist
1

n a person who expects the worst

Antonyms:
optimist
a person disposed to take a favorable view of things
Types:
defeatist, negativist
someone who is resigned to defeat without offering positive suggestions
Type of:
doubter, sceptic, skeptic
someone who habitually doubts accepted beliefs

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