What was your first boss you ever beat in a video game and how did you beat them?

The first boss I ever beat was the Wither from Minecraft. Either that, or Bowser from one of the Mario Bros. games.

I beat the Wither, but not after a bunch of OOFs. It was when I had finally gotten some diamond stuff (I may or may not have cheated [Hey, I was young at the time!]). I spawned in the Wither (Via creative mode), switched to survival, and fought. It was hard, and I died a bunch, but I KILLED HIM WITH MA BOE