WARNING: The following contains spoilers for Injustice: Year Zero #12, by Tom Taylor, Cian Tormey, Rain Beredo and Wes Abbott, on sale now.
In the cruel Injustice Universe, it's safe to say that it doesn't pay well to be the Joker's sidekick. In the Year Zero prequel, we learn how much he abused Harley Quinn, which informed why she'd turn on him later on in the game. This led to him using a new sidekick, Gary, a clear nod to Gaggy -- his first sidekick -- and since then, they've been on a rampage.
However, in Injustice: Year Zero #12, Gary's murderous run comes to an end when, as expected, the Clown Prince of Crime betrays the jester and gives him a most horrific end.
Joker loves killing sidekicks for the fun of it, especially henchmen who annoy him in the field. While Gary's not that incompetent, he's just in the wrong place at the wrong time. As he drives on a highway, Joker's trying to mind-control the original Black Canary to kill Justice League and Justice Society teammates aboard the Watchtower in space. However, Superman rescues them.
Doctor Fate also breaks the mental connection, which frustrates Joker as he knows that now the heroes are onto him, as he inches closer to his Amulet of Apophis. But the relic has other plans, speaking to him and reminding him there's greater power hidden somewhere, which makes him realize how expendable Gary is now.
Gary has a shocked lock on his face when the Joker says this, and the clown admits that his sidekick shouldn't have heard that conversation. As such, the Joker tells his driver to step into traffic, and Gary opens the door and jumps in front of a truck speeding in the opposite direction. He's immediately squashed in one of the series' goriest sequences as a bored Joker makes plans to travel to Egypt.
While Gary still did horrible things by helping Joker go after heroes, he didn't deserve such a cruel fate. Admittedly, it wasn't like Gaggy who got eaten by a shark in Batman: Three Jokers or Bob, a thug Joker always kills in his crew. Here, Gary was forced into servitude as Joker wanted a new Harley to boss around and abuse. However, this instance once more shows Joker doesn't care about his people and proves why it makes no sense to work for him since it automatically puts a target on your back.