All that remains for me to do is to leave.

All：主语

that remains for me to do: 定语从句修饰all.。（其中that为关系代词指代all并在从句中主语，remains为谓语，for me to do是残缺不定式，即不定式短语缺失动词或介词的宾语，空缺的to do的宾语在意义上由主语that填补。）

is: 系词

to leave: 表语。不定式符号to可以省略

本句相当于：What remains for me to do is (to) leave. 我需要做的事就是离开。