We use the adjective 激烈 to emphasize tension or resistance between two sides.
It was a time of intense activity
nà shì huódòng jīliè de shíqí
The fast food industry is incredibly competitive
kuàicān yè jìngzhēng fēicháng jīliè
Both sides got into a fierce debate
shuāngfāng xiànrù le jīliè de zhēnglùn
The adjective 强烈
We use the adjective 强烈 to emphasize strength and determination as well as a high degree or concentration of something.
For example, we use this adjective when we want to emphasize intense emotions, feelings, light, or color.