There are obviously so many classics to choose from, but I think "Close Your Eyes And Count To ****" by Run the Jewels ft. Zack De La Rocha is a candidate, definitely.
Provocative (leaning towards brutal), honest, exceptionally crafted lyrically, performed, executed and produced nigh on perfectly, and it summed up the feeling of the summer that it was released.
And De La's verse is just ridiculous