There are several viruses that live and exist on the computer. The best ones to pick for this question would be a virus that specifically attacks computers or any system connected to them.
The best answer is:
Viruses, Trojan Horses, Spyware, Worms such as WannaCry (which had recently caused some disruptions), and more can all destroy your files, delete your programs and alter your settings. Viruses replicate by inserting themselves into host systems that they attack while Trojans run damage operations from within their own operating cycles; Spyware which spy on individuals and send out information over the Internet without the knowledge of the person infected with it...