Hi WackyRabbit7

You can get all the agents PIDs by
ps -ef | grep "trains-agent"and kill -9 <pid> for the requested agent.

You can also pkill -f "trains-agent --gpus 0"   - This will kill a process that started trains-agent --gpus 0 .
Notice it matches the cmd pattern so it has to match the way you executed the trains-agent. This can be checked with  ps -Af | grep trains-agent