Similar to the I Win Card, the You Lose Card causes instantaneous loss for one or more players. You Lose cards are frowned upon, largely because they can bring about the end of a game prematurely or spoil a player's fun. You Lose cards may state explicitly that someone loses, or instead have effects that are so crippling/negative that they may as well state that a player loses.
For example, "YOU LOSE, YOU LOSER YOU", "This card cannot be removed. While in play, you can't make, play, or draw cards.", and "You must leave the game", are all You Lose Cards. Sometimes, people will play You Lose Cards on themselves because they don't want to play anymore.
Types of "You Lose" Cards
1. Direct statements, such as "You Lose Instantly".
2. Forced exits, such as "You must stop playing the game and leave".
3. Limitations on ability, such as "You cannot play cards".
4. Metagame Actions which are both used as a way to end play by defining a loss (or victor), and cause an intentionally biased game to be played so that the person who plays in a certain position in the turn order wins (with the correct strategy), such as "Stop the game and start playing Tic-Tac-Toe. If the game is tied in the end, then the person competing against the person who played this card loses."
5. Trap Cards which are caused by necessary actions, such as "You lose if you play a card".
6. Rules that are specific, and may impede play, such as "No drawing cards for any reason unless your name contains a W".
7. Cards which edit the turn order into skipping a player many times may be considered You Lose Cards. For example, "The turn order is now set so that the player on your right may only play one card every 100 turns. All other players continue as normal."