In Extremis we see an execution attempt against Missy. It uses a pretty high tech setup with stuff killing both hearts, and I believe the brain, simultaneously and they still are worried it might not keep a Time Lord permanently dead. It is also implied it took a whole to work out this killing method. This leads me to wonder about something Job Pertwee said in The Sea Devils to the Master who is currently imprisoned on a Earth prison.
Many were in favour of having you executed.
This suggests 1972 Earth could have killed the Master and both the Doctor and the Master seem to take the possibility seriously. This suggests the high tech method used in Extremis is a little unnecessary so could 1973 Earth have executed the Master?