Word for someone who expects something to go wrong

I'm looking for a word that describes someone who expects something to go wrong out of scepticism and doubt and disagrees ardently.

e.g. "I'm thinking that taking this route could be faster"

"It's not going to be faster(without knowing for sure)"

Solution 1:

Pessimist, defeatist, pragmatist.

I couldn't find an exact word, but hopefully these will help. If not, the word you used (sceptic) could work

I like naysayer

: one who denies, opposes, refutes, or is skeptical or cynical about something. {Webster's}

"There are always naysayers who say it can't be done."