By default, only Admin Users have the ability to delete deals in Pipedrive. Admin Users can provide the permission to allow for other users to delete deals by going to Settings > Manage Users > Permission sets
and enabling 'can delete deals' option for the intended permission set.
To delete a deal in the Pipeline View, click-and-hold on the deal you wish to delete, and drag it to the bottom of the screen. Drag and drop the deal to the DELETE button to delete the deal.