start a 2+ player server
press ` (default console button)
(type the following in the console IN ORDER)
--
sv_cheats 1
bot
bot_zombie 1
bot_mimic 1
--
after doing all those commands, line yourself up with the bot
run into the arena and press e (default use button)
if you did it correctly, you should be fighting the bot and the bot does everything you do
if you want the bot to face you type:
bot_mimic_yaw_offset 180
if you want to stop the bot from moving, type:
bot_mimic 0
ONLY DO THESE 2 AFTER ENTERING THE ARENA