After Dark of the Moon, we know that the Autobots where hunted down and killed by the humans following the battle of Chicago. But we never really saw Sideswipe die by the hands of humans. What happened to him?
According to the Transformers wiki, he was killed by Cemetery Wind offscreen sometime after the battle of Chicago.
However that was not sourced and all I could find was Michael Bay decided not to cast roles for Sideswipe in Transformers: Age of Extinction and again in Transformers: The Last Knight.