Nothing is 100.0% safe - but as far as I can find nuclear comes incredibly close[0] even when including Chernobyl and Fukushima.
https://en.wikipedia.org/wiki/2021_Texas_power_crisis
The grid came within minutes of overloading and shutting down completely, which would have required a slow and costly black start.
How about https://www.ferc.gov/media/winter-storm-elliott-report-inqui... ?
Even solar still requires various minerals the extraction and processing of which has environmental impact - like tailing ponds of toxic substances that frequently leak, particularly from earthquakes and extreme weather.
But to be clear, the human and environmental impact of solar, wind, nuclear and hydro pales in comparison to that of fossil fuels.
This isn't just counting immediate deaths - else it'd just be ~30 for Chernobyl and ~0 for Fukushima.
In fact, Fukushima's death count seems to primarily be down to that "people had died indirectly as a result of the physical and mental stress of evacuation" - which I feel should at least partially be put on the tsunami that killed 20000.