Seems obvious why its ranked the lowest.
Check it out:

According to a 2014 survey by the Office of Personnel Management, the Department of Homeland Security (DHS) was ranked by its employees as the worst place to work among the government’s 37 large departments or agencies, Congress was told Thursday.

The department, which includes agencies such as Immigration and Customs Enforcement (ICE) and Customs and Border Patrol (CBP), received an index score of 48 on global satisfaction in 2014, compared to a score of 62 in 2010. Last year’s score marks the lowest ranking of any government department that year.