もう少しで + [sentence]
もう少しで means "almost," "nearly," or "close to" and is used to describe a situation where something was on the verge of happening (but usually didn't), or where something is about to happen. It literally translates to "in just a little more."
The most common use of もう少しで is to describe a situation that nearly occurred – often something undesirable – but was narrowly avoided. In this usage, it is frequently paired with ところだった (was about to / almost did).
This pattern emphasizes how close the speaker came to the event. The implication is that it did not actually happen, and there is often a sense of relief.
もう少しで can also express that something is nearly finished or about to happen. In this case, the event is expected to occur.