What cancers usually lead to a swollen left supraclavicular lymph node?

Not the most: Common location, but primary lymphoma, breast, lung, esophagus, oropharyngeal head and neck sites, and then there is the stomach, when the node is called virchow's node.

Several: More common cancers leading to enlarged supraclavicular nodes include lymphoma (hodgkin and non-hodgkin), lung cancer, abdominal cancers such as esophageal and stomach, and breast cancer.

Lung, stomach: Many cancers can spread to the supra-clavicular lymph nodes, the common ones are lung, stomach, pancreas and cancers of the head and neck area.