Regarding the upcoming election of the next Hong Kong SAR Chief Executive (CE) on 2022-05-08: As of 2022-05-03, various news outlets report that John Lee Ka-chiu (李家超) is running uncontested. In theory, this could change in the next few days. For this Q&A, please assume that it will not change.
Is there a comprehensive list of uncontested elections for head of state?
Thinking more deeply while writing this question: This question may be more relevant for for presidential systems. For parlimentary systems, you would need to have all seats uncontested, then the Prime Minister would be virtually guaranteed, excluding party rebellion / split during gov't formation. (Surprise me! For example: Was Saddam Hussein or Muammar Gaddafi every elected, uncontested as head of state in a parlimentary system?) Also, I am not concerned about presidents in parliamentary systems (like Germany), nor prime ministers in presidential systems (like France).
I do realise the term "head of state" is complex. Take Australia for example: If you asked most non-Australians, they would not say (currently) Queen Elizabeth II. They would say Prime Minister Scott Morrison. It might be better to rephase this question as "the most senior/powerful executive positive". Another rabbit hole to consider: Finland has both (indirectly elected) Prime Minister and (directly elected) President that share power for complex historical reasons.
Finally, I am aware that only a small committee of about 1,400 people cast final ballots to elect the HKSAR CE.