Unexpected and really bad.
Beating can be a word for severe setback. Blow is another word for severe setback.
cramps
severe
Apyphony.
The suffix that means sudden severe bleeding is "-rrhage." An example of a term with this suffix is "hemorrhage," which refers to sudden and severe bleeding.
Gust is another word for a sudden strong blast of wind.
Panic, sudden, alert, are words for emergency.
small ;not major or severe
Another word for sovereign is severe and is used in a pacifistic way. Aplus answer independent.
U can call it depend on country. For example, Sudden Attack North America is SANA and Korean Sudden Attack is KSA
A word that means to depart suddenly is "plump" or "plumped"
severe, extravagant, strong, extreme