Word for a person with a negative attitude

What is the person called who always thinks negative? E.g.

Mr. X always thinks negative.

Mr. X has negative attitude.

What we can use either? Is there any particular word for this?

Solution 1:

The word is pessimist, a person who expects the worst.

Mr X is a pessimist.

Contrast with optimist.

It is often said that while optimists are happier, pessimists are more often correct.

and

Optimists are said to live longer than pessimists, though a pessimist might say those extra few years are bound to be miserable.

Solution 2:

There are a lot of colloquialisms and other terms that mean the same thing:

"Mr. X is a ..."

Negative Nancy
Downer
Drag
Debbie Downer
Naysayer
Prophet of doom
Doomsayer
Futilitarian

Solution 3:

Alternatives for consideration:

Cynic
Defeatist

Solution 4:

'Mr X Thinks negatively' is correct.

However, 'Mr X is a pessimist' is more grammatically sound.

Solution 5:

I've always enjoyed slang expressions like "Mr Unhappy is a real stick in the mud" (i.e. won't participate) and similar expressions like curmudgeon or party pooper. They have slightly different connotations than always thinking negatively, but I think the mindset would have the be similar to support them.