Actually, it used to be that the "deadliest" Marine was any Marine that survived boot camp...
Of course that was before the pussification and wokeness of the last couple of decades became part of the training strategies...
IAC, it is performance in combat that is the principle measure of the term "deadliest"...
Deadliest Marine?
Charles “Chuck” Mawhinney, more confirmed kills than Carlos Hathcock...