This one is quite easy.

Warlock's icon... Well, it looks like this:

What's the problem? Oh, as we all know, each and every hero has a portrait and an icon. A portrait is the "talking head" and the icon is, well, the hero icon. Most of our heroes' icons and portraits are nearly identical. They all share at least one thing: the direction the hero is facing. That is true for all of them, excluding 2 - Queen of Pain and Warlock. Queen of Pain looks right at the player in hero icon, whereas in her portrait she's turned slightly to the right. But Warlock... He's looking to the right in his icon - and to the left in his portrait.

Awkward wording, i know. Maybe it's just 11 PM.

Anyway, here's a TL;DR: