きゅうげき急激kyuugeki
1.

Describing a sudden and significant change or event that occurs rapidly and often unexpectedly.

2.

Characterizing a situation that escalates or deteriorates at a fast pace, highlighting the intensity of the transformation.

3.

Indicating a drastic shift in conditions or circumstances, where the degree of change is both swift and profound.

Example:

その党は急激にのびた。