People who are angry or upset about something.
Soreheads are usually not very happy and might complain a lot.
Examples:
The soreheads didn't like the new rule.
The soreheads always find something to be upset about.
The soreheads at work are always grumbling.
The soreheads at the party didn't want to play games.
The soreheads in the class never seem to smile.
The soreheads in the neighborhood are always frowning.