Whammy often implies a surprising and negative effect that is difficult to deal with. The unexpected tax hike was a real whammy for small businesses.
Pro Tip 2/3
Combination Hit
A 'double' or 'triple whammy' means multiple negative impacts are felt at once. The hurricane brought a double whammy: flooding and power outages.
Pro Tip 3/3
Colloquial Use
'Whammy' is informal and often used in spoken language or casual writing. Losing both the game and their star player to injury was a whammy for the team.