Actually there is no safe or safest operating system at all.
We need to check all of them for malware. Since the launch of the Pakistani Brain virus in 1986, the number of unique malware samples has exceeded 200 million.
Who is responsible for that, only the malware authors? To tell the truth maybe not. For example the developers of operating systems do not make patches in time, there are long delays, and as a result, a vulnerable state may remains for a few years.