How can you say "We have to let you go", in the context of firing somebody?
"我们必须让你走" is correct literally, but sounds straightforward.

You can use "不得不" instead of "必须" because it's more passive; and use "离开" instead of "走" to make the sentence euphemistic. e.g.


  我们不得不让你离开公司


Or make it more euphemistic by using "可能需要" (may need), (if you don't stick to the original English sentence and its translation)


  我们可能需要你离开公司