If you describe an activity as intense, you mean that it is very serious and concentrated, and often involves doing a lot in a short time.
The battle for third place was intense.
季军的争夺很激烈。
If you describe the way someone looks at you as intense, you mean that they look at you very directly and seem to know what you are thinking or feeling.
I felt so self-conscious under Luke's mother's intense gaze.
在卢克母亲审视的目光下,我感到很不自在。
If you describe a person as intense, you mean that they appear to concentrate very hard on everything that they do, and they feel their emotions very strongly.
I know he's an intense player, but he does enjoy what he's doing.
我知道他是个拼命三郎,可他的确是喜欢他所做的事情。