Terminus

Terminus was a a space station located (curiously) at the exact known centre of the universe. It was used by a company to treat Lazar's Disease. The treatment involved using the radiation from Terminus's engines in uncontrolled doses to remove the disease, often with a lethal amount of radiation.

The Doctor theorised that if Terminus' engines were engaged in their weakened state (after millions of years of leaking radiation) they could potentially end the universe. (DW: Terminus)