Actaeon had some great leadership skills, but his timing was just atrocious. See, while taking a break from guiding his buddies on a hunting trip, Actaeon caught a glimpse of Artemis as she took a bath.
Authors are divided on whether or not it was an accident. If it was an intentional move, Actaeon sure had some chutzpah. We mean, this girl is fierce. It also didn't help that he may have even bragged about being better at hunting than the goddess, which just… no. Terrible idea.
Either way, the result was the same. Artemis was outraged and worked through her anger by changing Actaeon into a helpless deer. He took away the secret quality of Artemis's grotto, so she took away something that he valued: his human body. Not long afterwards, Actaeon's own hunting dogs tore him apart, limb from bloody limb. It's a brutal end to a charmed life—but then, things don't typically turn out well for people who find themselves on the wrong side of Artemis.
So what should we make of Actaeon's transformation? Why did Artemis change him into a deer, of all things? (After all, aren't toads supposed to be the standard animal transformation punishment?) Well, for starters, the deer is one of Artemis's main symbols. By changing Actaeon into something that represents her, Artemis shows the young hunter who's boss. Sorry dude, you got served.
Plus, our friend Actaeon wasn't really known for his empathy or compassion. By the time he and his friends took a break from their hunting trip, they'd already slaughtered enough deer to land themselves on PETA's permanent blacklist. It's pretty fitting, then, that Actaeon is eventually changed into a helpless deer. For the first time in his life, he experiences what it feels like to be confused, scared, and powerless. Then, poor guy, he gets to see what it's like to be hunted and killed.