opposing sides
Two pairs or groups of characters are on opposite sides of the image and staring at each other, as if preparing to face off in a battle royals. Typically the viewer’s perspective is the side, so you mainly see the characters’ profiles.
Sometimes an image can depict only one side of the opposition. This tag is fine, so long as the other group is represented in a complementary image.
If it’s two individuals glaring at each other with malicious intent, use confrontation.