Candy and Harv.  
[Candela Solaris and Harvest Moon]
 
These two are the first non-alicorn duo to rule Equestria and frankly…they are the strongest monarchs to date.  
Their power comes from their benevolence and kind upbringing. While Candela loses her mother Celestia at a rather young age, a whole host of ponies help raise her to be the kind soul she is  
Even her exiled sister returns after the death of the elder Sun Queen to serve as a mentor.
 
Their reign at first lacks the polished maternal maturity but that almost works to their benefit. They are young and energetic giving Equestria the proper push to further extend the empires hope and productivity.
 
Without the people who loved and raised them, these two would have struggled to reach their full potential