Since update 3.35 we got the blacklisting feature. From the chat we can now blacklist players. Unfortunately this is only possible from the chat and not from the tournament page or the battle results page.

• Go to the chat.
  
• Click on the player's name.
  
• Click "Add to Blacklist"

Maybe you made a mistake and you want to remove a player from your blacklist. But how does this work?

You can't do this in-game. Therefore you need to go to the support page (online) of the game.

• Click on Support.

• Click on Profile.
  
• Click on Blacklist.
  
• Click on trashcan behind the player you want to remove.

That's it! 😉