Who is the Pyro?

Interview with Heavy

Mr. Deep: I read the manuscript of one of your earlier interviews. It said that you were frightened by, and I quote, "that thing,".
Heavy: Heavy did say this, but is taken out of context.
Mr. Deep: It is?
Heavy: Yes. Let me clarify. Baby is not scared of heights; baby is scared of fall. Coward is not scared of night; coward is scared of what's in the night. Heavy is not scared of Pyro; Heavy is scared of what Pyro does.
Mr. Deep: In your words, what does Pyro do?
Heavy: Imagine this. You are in battle. You are winning. You are unstoppable. Then, you feel heat. Fire covers entire body, charring skin and burning clothes. You scream in pain, begging for help. But allies are now black corpses on floor. And last thing you hear before ears melt off of head, is a sickening laugh that penetrates very soul.
Mr. Deep: ...The way you speak about him, it sounds like you view Pyro as an enemy.
Heavy: At times, yes. But most other times, I pay him no mind. I charge forwards with Medic, and Pyro does whatever he wants. He will burn his cowards, I will shoot mine; Pyro won't bother Heavy, so Heavy won't bother Pyro.
Mr. Deep: So you fear Pyro, but still hold respect for him not to get in his way.
Heavy: Da.
Mr. Deep: Well that doesn't answer my question, but I guess that helps.
Heavy: Would you like sandvich?
Mr. Deep: Oh yes. Thank you.