Often tied to some sort of milking machine.
Or both.
Rarely any consensual sexual scenes.

He originally appeared in the video game franchise Resident Evil (1996-), a member of a special police force fighting supernatural bogies. Later he joins a paramilitary group to fight bio-terrorism.
That explains the monsters, but it doesn't explain why this rather obscure character is so popular.
Some fans think that Redfield is canonically gay. He doesn't get a female love interest, and he's rescuing his sister, turning over the trope of rescuing the girlfriend.
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