Learn English – single word or phrase for “excessive humility disproportionate to ability or achievement”

I am writing a small biographical article about a long-deceased local doctor who served the poor people of this land meritoriously in the 1930's, and have composed this paragraph:

Dr.P was a medical giant and also a saint who thought himself just an unremarkable person; everyone was surprised at his excessive humility. For example, he politely refused a prestigious award in 1960 saying that "a mediocre physician like me, by no means a medical luminary nor even a special credit to the community, should not be awarded this honor for simply practicing his profession." On another occasion he told a friend:"I am highly overrated: all my achievements were fortuitous considering my ability; I just got lucky!"

I am concerned that "excessive humility/modesty" will be misunderstood as false modesty when what I really mean is excessive humility disproportionate to ability or achievement, as in these real life examples:

(1) One of the greatest ghazal singers, who performed in my home city 2 years ago, told the adoring audience:

"I am just a small and humble singer. Your love has elevated me to such a high position.

(2) In an interview after playing one of the greatest batting innings in cricket history and making a huge personal score that led his team to an improbable victory, a great Indian batsman said:

"I am only a supporting batsman in this team of great players. I just wanted to occupy the crease, play out a lot of time and score runs whenever it was safe to do so. My friend who is a great batsman was very supportive from the other end. I am more happy that my team won this Test match."

This is not false modesty but real and profound expression of humility from a great achiever. In short, the doctor persistently and genuinely considered himself ordinary & mediocre when it was so obvious to others that his achievements and services were extraordinary. "Almost a sense of unworthiness which was very surprising", someone said. It's this sense that I am trying to highlight in my sentence. Is there a single word or phrase that conveys that meaning?

Research done: none of the synonyms of humility at Thesaurus.com, Merriam-Webster and Collins Dictionary seem to precisely express my meaning. What comes closest is the adjective self-effacing and also the noun self-abnegation, which carry some negative tones and may not be appreciated by the home audience, which reveres this legendary doctor.

Sample sentence for SWR (will not be used in this exact way in my article but is illustrative here of the word I seek):

Dr.P was characterised by excessive humility disproportionate to his high ability and achievements: everyone was surprised by this ______________

Note: adjectival forms are also welcome if the word or phrase doesn't have an appropriate noun form; I shall rewrite my sentence accordingly.