…死了【sǐ le】

死了 after an adjective pushes it to the extreme, like "to death" or "so" in English. It is casual speech, and it mostly goes with feelings you'd complain about: tired, hungry, hot, annoyed.

With a person in the middle

With verbs of feeling, the person affected can go between 死 and 了. 气死我了 is "it's driving me mad".

Good feelings too

A few positive words take it in very casual speech, mainly 高兴 and 开心.

Where it goes wrong

死了 already says "extremely", so it takes no 很 or 非常 in front.

• × 我很累死了 → 我累死了

It is too casual for writing or for a polite complaint at work. There, use 非常 or 特别.

• × 这次会议的时间长死了 → 这次会议的时间特别长