Run this sql statement to force an agent into Inactive status.
psql -h localhost -p 7432 -U Skybot -w -d schent2 -c 'UPDATE agents SET runtime_state = '2' WHERE name = 'xxxxx'';
where xxxxx= the name of the agent you want to remove. Please make sure customer backs up database before running the command, just in case.
there are 3 runtime_states, they are 1=active, 2=inactive, 3=failed