Would Resemble:: Joe Biden
Kevin Garnett can be seen as an arrogant, loud mouth yet loyal individual. In many ways, Joe Biden can be considered the same thing. Both guys have the tendency to just fly off the handle and say whatever is on their mind, regardless of whom it may offend. Sometimes, it may be to get a rise out of the opposition.
In KG's case, does the Honey Nut Cheerios situation ring a bell? As for Biden, did you see the way the Vice President handled Paul Ryan in the VP debate leading up to the 2012 Presidential Election? However, both Biden and Garnett get a bad rap. They are simply passionate men towards their respective field of interest. For Garnett, it seems as though when he sets his mind to something, he dives in headfirst and remains tried-and-true to a fault.
If KG were to go the political route after retirement, he would be extremely loyal to his party while striking fear into his competitors. He wouldn't have a single problem doing, saying, or acting in whatever way is necessary. Those in his party would love him while the ones on the other side would despise him. And honestly, Garnett would not want to have it any other way.