9. Abandoned Speedy To His Addiction - Snowbirds Don't Fly
Comic books don't tend to shy away from real-world problems. Many embrace issues across the board that we normal humans have to deal with on our own.
For the Green Arrow, a massive issue came in the form of his partner and protege, Speedy, who ended up forming a heroin addiction. Speedy even sold several of Oliver's own arrows to junkies in order to score more of the highly dangerous and addictive drug.
Those arrows ended up being used on Star City's protector, severely wounding him, and all because Oliver went on a cross-country road trip with his best pal in spandex, the Green Lantern.
By leaving Speedy alone and unsupervised, Oliver allowed his partner and young ward to become an addict. This specific story put the character of the Green Arrow back on the map, showing that the hero and his writers were willing to deal with all kinds of hard-hitting issues that affect people across the world.
However, this story is also one of Ollie's greatest failures as a mentor, friend, father figure, and hero to those in need.