The line comes from Team Fortress 2, the class based shooter released by Valve in 2007, where the Heavy is the large Russian minigun specialist voiced by Gary Schwartz. His short taunts were widely ripped and shared on forums, video edits and soundboards during the early meme era of the game. This particular wording became a reusable reaction because it sums up an expected loss in a few words. It remains popular in gaming clips, remixes and chat soundboards long after the original match context has been completely forgotten by most viewers.
About this sound
Voice line from Team Fortress 2 where Heavy says you are dead, not big surprise, used for fail moments, gaming deaths and meme reaction edits.
This is the Heavy from Team Fortress 2 delivering his blunt death taunt, you are dead, not big surprise, in a deep Russian-accented voice. The delivery is slow, flat and completely unimpressed, as if the outcome was obvious from the start. The dry insult lands harder than a shout because he sounds bored by your failure. Creators use that deadpan tone to mock obvious mistakes, predictable deaths and overconfident plays, letting the line do the roasting without any extra commentary or reaction needed from the player who just lost badly in the clip itself.