Final answer:
The common characteristic of the most serious cancers is their ability to metastasize, leading to the spread of cancer and increased severity of the disease.
Step-by-step explanation:
Cancer is a group of diseases involving abnormal cell growth that can potentially invade or spread to other parts of the body. One general common characteristic of the most serious cancers is their ability to metastasize, which means the cancer cells can break away from the original tumor and establish new tumors in other organs. This process can lead to the spread of cancer and increase the severity of the disease.