bot_autodifficulty_threshold_low <number>
The game scores every player by how much they contribute (kills, objectives, etc.). When a bot scores this many points below the human average, the game automatically raises that bot's difficulty so matches stay competitive.
Examples
bot_autodifficulty_threshold_low -2 - Default. A bot has to be 2 points below the human average before it gets buffed.
bot_autodifficulty_threshold_low -5 - Bots have to be 5 points below the average before they get buffed.