I’m inordinately fond of Professor Samuel Oak himself as a former badass-turned-researcher in an estranged relationship with a distant grandson who’s name and face he’s forgetting more and more often. My headcanon which is adapted from the ever-lovely Crow is that when he was younger, the strong and handsome way Agatha likes to remember him instead of the ‘old duff’ struggling with early onset Alzerheimer’s that he is now), he was practically killing it in the league and was a champion for a while (balancing his studies/university work as well).

He was instrumental in bringing down an up and rising crime boss named Giovanni the first time around (His Charizard was killed in the battle) and was devastated when politics, money and corrupt officials allowed Giovanni not just to go off on the light sentence of community service, but claim a gym as well.
It’s partly why he moved his entire research center to Pallet town (so he could keep an eye on Giovanni’s operations) andwhy he’s pretty hard on Gary whom he hopes in his old age and fading mind to be able to take care of himself when Giovanni decides to target his family and/or finish this rivalry.
Giovanni’s revenge on him has been to fund pundits to discredit his work and make him out as too senile to lead the nation’s science department, even going as far as to revise what actually happened during their clash to favor Giovanni’s version of it—-things became bad enough that at one point, Gary himself volatile and desperate to step out of his grandfather’s shadow actually believed the propoganda.

His son was Gary’s father, and as it stands, he can’t remember much of said son or the wife (they died in a car crash which landed him with Gary and Daisy) and that terrifies him especially when his memory of Gary has gaps in it as well—he’s trying his best to keep his memory sharp by continuing to work on and impart to promising youth what he believes matters in Pokemon training and hold on to whatever of his mind he has left.