A couple of years ago the bot situation in casual Team Fortress 2 was so bad that it wasn't uncommon to land in a game where the majority of at least one of the teams was a group of cooperating bots. In those matches you have the possibility to start a kick-vote on your team mates, and those bots would immediately vote “no” if you tried to vote on any of them and because they were the majority of the team these votes always failed. And if these batch were in your enemy team all you could do was to ask the remaining, hopefully real, players on the enemy team to try to kick them. It was especially annoying when you tried to play certain game modes these bots weren't programmed to handle, they had no idea of the objective and the match would stall indefinitely, forcing you to queue for a different match. And if I remember correctly these bots were pretty much headshotting everything they got in sight. Something the server can easily detect. But VAC for example acts intentionally slow, so cheaters don't get immediate feedback.

Out of curiosity I did a quick internet search and a couple of months ago a new wave of bots has emerged. Those bots also join as majority group but never fully join the game, they simply take up slots in a team, preventing others from joining. Makes you wonder why the server isn't timing them out.